I've used System 3 Marine epoxy, System 3 Silvertip and Marinepoxy from Bateau.com. Silvertip is my favorite because it wets out the best, has the least waste (still useable even when the cup is hoy in your hand) and has the strongest mechanical properties (especially if you post-cure it). It's also the most expensive (of course). With epoxies, you generally get what you pay for.

Elmer's is a polyester resin, not an epoxy resin. It's totally unsuitable for use on modern stitch and glue boats. Polyester gives off styrene gas as it cures, does not bond well to wood, shrinks as it cures and is porous when cured. Its mechanical properties are inferior to epoxy's (not as stiff and softer).

Laszlo

I have used MAS epoxy with both the slow and medium hardener. The two hardeners can be mixed in any ratio to customize the curing time to the temperature. It is important to keep the ratio of resin to total hardener volume to 2:1, though. If the slow hardener is used it wets out fiberglass well and does not leave any blush. Depending on how much medium hardener is mixed in you may get some blush so I only use it when I am gluing. I don't have anything to compare it to, but I also see no reason to change.