The time I like to raise a hand like ATs utg or even KJs, is when I believe many people are gonna call me with worse hands. I like the idea of buiding a large mutiway pot with these hands. If I believe my raise will only get called by 1 or 2 players or I'll get 3 bet and be against 1 or 2 players, then I would rather limp with these hands as I would rather play these hands 6 or 7 handed for one small bet OOP than 2 or 3 handed for 2-3 small bets OOP. On rare occasions when I think an UTG raise will win the blinds, then I will raise in that situation also.
There are many 2-4 games where it would be correct to raise with ATs utg, and there are many where It would be correct to call.
In general, if you have no read on the table, I think it would be better to call UTG than raise, but thats just my opinion, as I have no hard data to back up any of my logic in this post.