I'm definitely preferential to Kadees, but will use the plastic couplers until they give me trouble.

My one beef with Kadee is that they discontinued the 40-series in favor of the 140-series.  I liked the flexibility of the old standard shank, that I could use both with the bronze centering spring, or the 30-series torsion spring.  I can still use the 20- and 30-series couplers, but that gets back to the issues of plastic couplers.  Yep, those ARE plastic!

-Fuzzy
 

I've had 20 series couplers on a couple of engines with tight clearances for many years, and find their performance identical to the all-metal Kadees. The tolerances of the coupler and the density of the plastic shank are such that they do not do the McHenry trick of deflecting up or down when a heavy load is placed on them. YMMV but you will most likely not have problems with them.

Sergeant have a Rotary coupler listed. Never used them so I am not sure how good they are.

I saw a layout at an exhibition once that had a rotary dumper. They used a some sort of jewelry swivel. I would look at Hobby Lobby or similar. 

If you want a real coupler that works and doesn't have the bounce between the cars you get Sargents couplers and you can buy in bulk and get the right coupler for the time period and it looks better and operate better it put Kadee back in the dark age I just don't understand why everyone want what is out  of date for there trains.

 Mike

 I just don't understand why everyone want what is out  of date...

I have a large layout where we handle some 400+ cars a session, with a need to couple deep into yard tracks, as well as to have reliable automatic coupling in staging, often well out of convenient reach of the staging operator.  Sergent couplers aren't especially friendly for operation like this compared to Kadee.

"Sergent couplers aren't especially friendly for operation like this compared to Kadee."

   I was gonna tell him that but I figured he'd find it out for himself once he started operating :>) ......DaveB 

Mike, what is this bounce you are talking about, not sure that I have seen it?

 "this bounce" 

   My guess was slack action ? Which being an old caboose rider I kinda enjoy seeing in my toy trains.......DaveB 

There's a fair amount of slack in the standard #5 knuckles. Not so much in the #153/#156 etc "scale" heads. Sargents require pretty good access for coupling and uncoupling.

Real trains have slack action as well. At least they did in the Steam era, one always hears about taking slack or bunching the slack as the case maybe and that is a nice feature on long trains.