I'm a cheapskate and I'm just about to buy my kegging setup. Due to being cheap pin lock kegs seemed to be the way to go since they are a good 30% cheaper virtually everywhere. BUT there seem to be 3 significant conveniences that ball lock offer which I think will justify the extra cost.
1. Pressure relief valve. I know it can be done on pinlocks, I'm talking pure convenience here.
2. The ability to seemingly always be able to fit 1 more ball lock the pin lock. I dorked out and cut several 9" circles (pin lock width) to figure out the best configuration. I can fit 3 pin locks on the bottom shelf, but I can fit 4 ball locks. And the ability to grow seems to be another necessity w/kegging.
And the ability to clean the ball locks like in this video are what pushed me all the way out of my cheap state of mind just for once.