I've bounced back and forth between split and 3 under. Accuracy may be slightly better shooting 3 under, but I just don't feel that I have control of the arrow as well, especially for hunting conditions. I know it's all mental, but that is mostly what archery is. I also find that 3 under is louder TO ME. I don't know that it makes a lick of difference to game animals.
I feel confident shooting split, so I think I'll stay that way.
BTW: If you are raising your brace height an inch or so higher to shoot three under, you are reducing the performance of your bow about as much as you would by adding cat whiskers or another silencer. Again, though, I don't think the deer will notice the difference.