SRAM chains rule - I run one on my Shimano 11spd road system and the ability to field repair with a speed-link is key. It's a must have part for any repair kit.
The Powerlock link is outstanding. I bought several of these to make traveling with my bike easier. Now, I simply take the chain off when I disassemble my bike, clean it, and place it in a plastic baggie before packing my bike in my bike bag. The Powerlock links make reassembling the bike, and chain, extremely easy. I keep a Powerlock link in my Continental seat bag as well as in a Stickypod bike bag that I place in a jersey pocket. The Powerlock link makes fixing a broken chain simple (not that broken chains occur very often, but having a link that can fix the problem in a few seconds is well worth the few dollars that it costs).
Been using SRAM Powerlock Links for several years, but with 10 speed chains. Finally switched to 11-speed and bought two with my build kit. The first one I put on was very very tight and caused a problem with the chain passing through the rear derailleur. Replaced it with the second one and worked like a charm
I've never had the problem with them being tight on 10 speed chains and I suspect that I just unfortunately got a bad one.