there isn't a ton of information but, in general, it would depend what position the original raiser is and how they're playing.
if it's utg and they're a tight player, i'd rather flat call and play post flop.
if the raiser is in late position like the co or btn and they're opening a lot from late position, i'd lean more towards 3betting as a squeeze play. i'm not really concerned about the other flat caller, unless they're just super nitty and flats with jj-qq. so, i likely have the range advantage over the flat caller and potentially the opener, but i want to isolate with the initial raiser and go heads up as my range advantage is much better against 1 opponent vs multiple.
by squeezing, i give myself better
odds to win the pot. either by all players folding or isolating and seeing a flop with better
equity. and even if i still get 2 callers, i'm probably still slightly ahead. at worse, i get 4 bet and i have to decide what to do. or i see a bad flop and have to check/fold vs 2 other players, but i still allow myself multiple ways to win the pot, either uncontested or by having the better hand by the river, which is an advantage i wouldn't have if i just flat.