How many times have your fingers slipped off the L2 and R2 buttons of your Sony PS3 Controller and always at the crutial moment in the game. Real triggers put a stop to that happening ever again. Simply put if you use a Sony PS3 Controller and serious about your gaming you should use these.
They slide/clip on to the convex triggers and add a concave curve, helping your fingers stay securely on the trigger buttons
Other than adding security for your fingers, that's about it. If you want to revert back to the old triggers' feel, removing the clip on triggers couldn't be easier.