The Kadee #5 is still an excellent coupler choice, even better are the #148 or #158 "scale" size couplers.  The #148 combine the #5 coupler with the whisker built in centering springs.  The whisker springs save you the trouble of finding ways to stack the bronze centering spring and the coupler into the box and put on the cover and then fasten it all together with a screw.  The #158 is closer to a scale coupler head, but the track work has to be perfect to use them.  If you have any dips and bumps in your track work, you will experience nuisance uncoupling.  The rack work and coupler heights must be good with #148s, but #158's are even more critical. 

My plan is to use Sergents on my home switching layout, but I would not consider them for or the #158s for use on the modular club layout set ups.  The dips and bumps that seem to be standard with modular layouts that are set up and taken down repeatedly seem to invite nuisance uncoupling without adding to the problem with small coupler heads.

Forget the non-Kadee "knock offs".  When Kadee's patent expired, many manufacturers came out with cheap plastic versions of the Kadee #5.  They look good, but don't do the job.  Their primary "advantage" is that they are cheap.  The shanks tend to break and if they have the plastic leaf springs the springs tend to "take a set" if laid on their sides, and they don't hold the coupler closed reliably with more than 2 or 3 cars behind the locomotive.  Many of the manufacturers who originally came out with the plastic leaf springs on their couplers have since switched over to metal coil knuckle springs, but none have addressed the problem of basic weakness in the coupler shank.

I use Kadee #58's (or 58 series) couplers on all my rolling stock as soon as I can replace the #5's or similar couplers.

I use the MKD's on everything HO that I have built--a lot of 5's, but some 4's and others.  I tried the knockoffs and found the plastic "springs" take a set when cars using them are stored on grades with the loco on the downhill end and will not couple properly after that.

MY Sn3 stuff used a lot of MKD-4's for the kits and 5's for the scratchbuilt cars.

I found the easiest coupler for manual uncoupling is the original KD couplers as there is no hook on the coupler unlike all of the magnetics.

I have about 200 cars built for a railroad that will use only 20 or so cars so I'm not planning on making any changes.

The Sargent's look tempting, but testing them is quite far down on the project list.

Terry

but in my experience, Sergents stay coupled in all track conditions, far better that any of the Kadee types.

That said, they are strictly prototypical, and so don't have many of the "model operations" extra conveniences like self centering, or easy coupling slight off center on curves. You also have to make sure the glad hand is left open on at least one coupler to enable an automatic coupling.

But uncoupling with the wand is easy and positive, without need to touch either car. None of the issue that skewers have. And boy do they look good!

If you want to get a good sense of what's standard, walk through a train show.  By and large, it's Kadee #5s. 

Sergeants are here, but they're still a niche.  They may become stronger, but with the strength of Kadee in the market, I don't see Kadee going away any time soon.

My program with the plastic knock offs is "run until failure," especially if they have the coil spring instead of the whiskers.

The layout runs fine on Saturday morning, but things move about and by Sat evening or Sunday morning we have difficulty keeping trains with #5's coupled through some of the joiner tracks.  We end up shutting down the layout for a few minutes to readjust and re-level the layout at the joiner tracks.  Also being a club it is difficult to get modelers who only buy and run r-t-r equipment to deal with manufactured rolling stock that has the wrong coupler height.  In addition long cars with a lot of end overhang don't like any sort of dip or bump in the track work.  Some guys run the #158's, but most run the #148's or #5's just for the added reliability.  I also realize that a modular club is a totally different animal than a home layout that doesn't move and doesn't get taken down and put up and transported all of the time.

Being new to the hobby (started in 2008), I decided to go with Sergents. I love(d) the look of them, and I was frustrated with uncoupling kadees (either by hand or magnet).  Undoubtedly my frustrations were due to lack of experience, but they existed nevertheless.

I also really dislike the bouncy action of Kadees, with 12 cars behind a loco, the last two will stretch and contract as the coupler slack and play come into effect while running. Visually it ruins it for me.

My experience with the Sergents has been very positive. Being new, I didn't have many barriers to adoption (cost of upgrading a fleet, or interchange concerns).  I think they stay together much better over rough track than kadees; the mounting heights can even be fairly off and they'll work. They couple cars together closer for better appearance as well.

The only "problems" that I face with them is if I've put them together incorrectly.

Sergents are not for everyone, if you have trains you can't easily reach, interchange cars with other modelers or clubs, or have a huge fleet to convert, I'd advise careful consideration (or for the last factor, they do now offer bulk packs that cuts the cost substantially).

On my fleet of HO scale equipment Kadee couplers have proven to be the best for me. Whether you opt  for the scale coupler, the whisker coupler or ol reliable #5 it is money and time well spent. Walther's has introduced a Kadee clone coupler similar to the #5 and I have just recently installed them on some later purchases. So far so good. No matter what coupler you decide on the couplers are only as good as their installation.

Good Luck

John R   

The only "problems" that I face with them is if I've put [Sergent couplers] together incorrectly.

I had a similar experience.  I have tried Sergents, and had planned on putting them on my entire layout.  About half of my rolling stock still has them, though I am in the process of replacing them with Accu-Mate Proto couplers.  I ran into two problems.  One was the absolute necessity of replacing every coupler, and usually every coupler box, on every piece of rolling stock before it hit the layout.  As I acquired more cars, that became a hassle.  The other was that, since I was putting them together myself, quality control was not perfect (it's not easy to get just the right amount of glue without getting to much - it takes experience) and I had a number of couplers fail either by falling apart or no longer operating.  A third, somewhat less significant issue, was the inability to operate my cars with anything else on another layout.

To me, Sergents are one of those brilliant but slightly impractical ideas that I really, really wish would have worked out better.  They look incredible.  As a railroader, the look and function is what I am used to at work, and I have no problems with the lack of centering springs.  The close coupling is superb, and the uncoupling is by far the best and most reliable of any coupler I have found..  If they were available ready to install for a price more in line with Kadees, I might still be using them, especially now that they have designs made to fit a #5 box.

As for the best coupler, there is probably no simple general answer, as it depends on what you want.  I like the Accu-Mate Proto couplers because they fit the coupler boxes I had previously installed for Sergents, they look pretty good, they're cheap, and they operate with Kadee and Kadee clones.  If a car already has one of the clones on it, I leave it (usually cutting off the trip pins).  Since my layout is small and my trains short (5-6 cars at the absolute limit) the strength is not a major concern.  I have also found that the different couplers operate differently, specifically when using an uncoupling pick.  Some work better with flat picks, some with round picks, some with different techniques.  Using a pick to uncouple swing knuckle designs (like Kadee) has never worked reliably for me, although I have no problem at all with the split shank design (like Atlas and Accurail).

So you may want to try some different couplers and see what you like.

The WRMRC layout, like most large clubs, is 100% Kadee coupler equipped. The bulk have #5's installed due to their age, as scale #58's only came out a few years back. Most new locos and cars now either have #58 scale couplers or #158 'whisker' couplers. We can report there have been no uncoupling issues even with the coupler-mixing. All work great over all turnouts whether hand-laid or pre-fab, and (more importantly) those crazy helices.

^{The #158 is closer to a scale coupler head, but the track work has to be perfect to use them.  If you have any dips and bumps in your track work, you will experience nuisance uncoupling.}

Sorry to be blunt, but this sounds like you have issues with trackwork, or not complying with NMRA coupler heights, or a combination of the two. There are only 2 millimeters of height difference between a #5 and a #58/158.