Can't recommend the Sergents enough. I converted to them from Kadee about two years ago. Of course it was the old style Sergents which were harder to put together and didn't operate as reliably as the new ones. I received some prototypes of the new style (EC87) a few months ago, and I must say they put the old ones to shame, and the old ones put Kadees to shame!
I have never had one coupler break or uncouple in normal usage. That is to say I have accidentally broken one due to my own stupidity (glued the knuckle to the body and tried to pull it apart; oops). Sergents couple together much tighter than Kadees, which virtually eliminates uncoupling due to slippage. I've had horribly mismatched coupler heights cause no problems. Mine have survived bashing together and drops to the floor. I've pulled a 70+ car train with three locomotives up 2% grades and around curves on the club layout with no problems. Got lots of interesting comments about the 'tiny' couplers though!
The only 'advantage' that Kadees have is that they can be smacked together and always couple. Sergents need to be lined up and have one of the knuckles open to couple, which is just like the real thing! I'm definitely a fan of the slower paced, more prototypical operation of the Sergents. Sergents can couple to Kadees automatically, and uncoupled with a bit of fudging, though it does create excess side pressure which can derail light cars.
The EC87 coupler is flawless in appearance and operation as far as I'm concerned. None of the other "scale" couplers come close. (Are Kadee/McHenry/Accurail/etc. ever going to learn that trip pins/springs/flopping knuckles are hideous?) After using Sergents for a while now, I can barely stand the sight of Kadee #5's..
