i gotta say that i'm one of these cats that fits in-between the cracks of both Epic and TGR.
i had a blast at the Tahoe Gathering recently, but spent most of my time riding with Cirquerider, Scotskier, and X-Eastcoaster (no disrespect to those i didn't ride with, though. These are the folks I gravitated toward both in terms of skill level and personality. That said, everybody I met from Epic at the Gathering was cool and i had a blast at least tailgating with those I didn't ride with).
this past weekend i "indulged" in a Maggot day @ Kirkwood. The TGR folks I met through X-Eastcoaster (Skier666, Arty, and others) were all ripping skiers and seriously humbled me. they were gracious enough to let me tag along with them on a bootpack to Thunder Bowl and didn't laugh when I handlebared on the virgin crust-on-fluff. Nice chaps on the whole, but a bit more rowdy than the Epic crew. Later in the day I met Tryrone Shoelaces and even Splat of PMGear fame, who offered me the chance to demo the infamous Bro in a 179 (sadly i was so beat from the bootpack that I declined).
personally, I like splitting my time between the two camps. there's valuable info to be learned from both, you just gotta read between the lines and suss out who is really on the level and who isn't.
so far all i've met in person and have had the distinct pleasure to ride a whole day with have been great, both from Epic and TGR.
but if you want a simple answer I would go with this:
Epic: predominantly ski on planks less than 87mm wide of variable lengths (for example, other than Cirque and X-EC, all the Epic folks I have met to date were riding skis in the mid-70mm-to-low 80mm range)
TGR: predominantly ski on planks greater than 94mm and no less than 180cm in length
(for example, all of the TGR folks I have ridden with to date were on nothing narrower than a 99mm ski, most were well up in the mid-to-upper 100mm range, even on hardpack groomers).
i felt that i was riding "wide" with my 94mm King Salmons amongst the Epic heads and that I was riding "narrow" with the same skis amongst the TGR peoples. Then again this is just a generalization as I know some TGR folks who have narrower skis in their quiver (still usually nothing narrower than a 78mm, though)
but again, i can't stress enough that those i have met from each faction have been cool, gracious, and a pleasure to ride with. they've also taken me into terrain i might not otherwise have thought to scope out and have been patient with my quasi-gaper steez to no end. for that i am eternally grateful and urge each and all to hook up with some of these folks whenever the occassion arises.