I'm not the expert in Treasure Maps, but I would guess there a two cases:
a) You're up to some Village-Smithy-type draw engine: In this case you hopefully can play your TM while you can still redraw some cards, so the question is not really relevant. Hopefully you can or have played some card with +buy. Otherwise it depends, but more money is probably not helpfull, you now have $12 in Gold, so the chance is high that you can reach $16 which would be Double-Province. If you really have trashed everything else and and don't have any cards that gives money, buy a fifth gold and afterwards something that pushes you above the 16. Building up to more is often not nescessary. So either you need more Enginecards, than buy them, otherwhise a Province might be something you want to take, depends on when you reshuffle and how many are left.
But probably as I said it's optimal if you can still in this turn get some of the gold, or all if you have played some +Buy.
In Colony, I'm not sure I want TreasureMaps.
b) If you're more up to some BigMoney strategy, than I would take the Province. You have 4 Gold, that should be enough.