I like pin locks, but I wish they had a pressure relief on the lid like the ball lock units.
Pin locks rule! I ended up getting some pin locks for free, so that's what I use. The parts aren't as easy to come by, but they're still relatively easy to find. No problem with not having a manual pressure relief valve, I just depress the gas poppet with a little screw driver (or whatever is handy) When it comes time to increase my keg collection, I'll probably buy more pin locks just so I don't have to buy different disconnects
I use ball lock because I got on a board full of people adamant that this was the way to go. More people sell them, and therefore parts and connectors for them too. And since I've never even seen a pinlock, I don't know what I'm missing and am happy with what I have.-OCD
[Next time you accidentally put the gas line on in the "Out" post on a beer that has been lagering for 4 weeks and you blow sediment all up into your beer you will know.