Graham;191274 wroteFold because of the flush draw, without that I'd ship.
Definitely, on a rainbow board we have a monster and we should gamble. That pesky flush draw makes it a tough decision though. By the sounds of villain #1, if he has a non-nut spade draw, he won't be folding it. People with a mainly holdem background will see the pot odds (3:1 or so if you call) and 2 spades in their hand and rarely think that they could be up against a higher flush draw.
We very likely have the best hand at the moment, 33xx showing up here is pretty unlikely. Given their aggressive natures from a holdem background, there is enough of a chance that at least one of them is going nuts with subpar (ie, non-drawing hand) like AAxx, to swing this to a call.