It's no secret to anyone who knows me or has read my posts, that I'm huge fan of the SEAL and yet if forced to chose between the two, I'd take the EZM1. Not only is it incredibly rare, but it uses the much-loved and now discontinued Lemania 5100 chrono movement on one of the cleanest dials this side of, well, a SEAL (gotta love the red font in the date window...).
The above notwithstanding, how exactly do you intend to use the watch? In terms of out-and-out toughness, the SEAL is gonna take this fight, but if you're looking for more all-around piece, the EZM1, by virtue of its chronograph, lower wrist profile, and lighter weight is a more versatile watch.
I say, if you've got a bead on an EZM1 for sale, and the price is right, jump on it.
PS - Otherwise, get the SEAL ;-)
Yeah, if you've already got an EZM1, hold on to it with two hands and don't let go! As for used SEALs, they don't come up for sale very often, and when they do they're usually snapped up pretty quickly. The best route would probably be to place a Want To Buy post on the TZ Sales Corner and Watchnet's Trading Post, and see who bites. In my case, I just waited until one popped on on TZ, though I will confess that it took a while (I was waiting for a relatively new one on a bracelet, and with the wooden presentation box). You can also try eBay, as they do show up there once in a while. The good thing about Kobolds is that no one is building fakes -- yet -- so as long as you trust the seller, you're pretty much guaranteed to get the genuine article.
PS - DO NOT let that EZM1 go...