I like the sturdyness of the V1 slide on. You can use one hand to slide it into position and let go of the TSO along with whatever junk you have attached to it, and clip it. The V2, requires 2 hands or you place it on the table. Which still honestly takes two hands because trying to clip it sometimes knocks it out of the groove unless you hold it in position with the off hand.
It is useful though to just clip on when using the MFT and you happen to have a rail protector in the groove that excludes the possibility of just sliding on the old V1. Most of the time, you want this near the end of your rail anyways so I'd vote V1. Unless of course you're cheaping out and attempting to use it for both end PGs, which having one clip-on may be useful - or you can just go and buy the separate PG clip adapter.