If you like the 510C than the 512 is the same thing just enclosed. I still prefer the Aimpoint-style ones with the dial though. The dial makes them foolproof so you don't start a stage by accident with your setting being messed up, and they're a tad brighter. Plus, I like the round window... I used to use the circle-dot reticles too for a while but found later that I'm faster and more accurate with just a single-dot (but I do kind of think the round window creates a somewhat similar fast-acquisition effect for me, which is why I think I also like the SRO's).
I've never had a problem with a Holosun holding zero or any issues at all other than I once got a 510C that had the "ghost square" issue the MRO HD's get (I just sent it back and exchanged it for a different one which was fine). That said, I've heard a few peeps more recently mention that the more recent ones are spotty QC-wise more so than they were when they first hit the market years back.
On the bright side, for a game gun, the Holoson's are cheap enough that buying a backup for "just in case" isn't as painful as usual.