If you want a nice system with great SQ/SQL, spend less time worrying about the relatively subtle differences betwen those subs, and more time researching/building/fine-tuning the install. Seems silly to me people get so carried away worrying about which subs will sound 'better' and yet concern themselves very little with getting the install just right (not saying you are doing this tiger). There's much more to be won/lost in terms of SQ and output in the install than there is between those two subs. That goes double for the amplifiers.
Like Punk said, which sub will blow at X number of watts really is a non issue. If you were comparing a 100watt sub and a 1600 watt sub, yes Id place a bet the 1600 watt sub has more potential. But when you are comparing such closely related specs, which melts down first really doesn't need to factor in. Maybe one sub blows quicker, but due to higher efficiency is also producing more output than the other can when it blew. More output, fewer watts to buy, sounds like a win-win situation. Im not saying the IDMax is more efficient, I dont know. But I am saying a discussion like this shouldn't ignore that possibility. And Im just assuming you are talking about thermal power handling alone, as mechanical power handling is closely dictated by the enclosure.