Thomas,
Essentially, the Gorilla is the Miniposa with stronger fabric and an aluminum stay.
I just tested out (at home only) the Ohm and the Gorilla. I choose the Gorilla in a very very close contest for the comfier hip belt and shoulder straps. It took me 2 weeks of nightly packing and testing to get each bag dialed in, but when I did so, I took each up to 35 lbs, wore than for an hour, and both passed the test. For lighter weights they were both great. I'd give the Ohm a slight edge in carry. (The load lifters allow for more tweaking than on the Gorilla) but that was somewhat negated by the less comfy hip belt of the Ohm. I did get it to where I could wear it comfortably, but I was concerned that out on the trail, it would require frequent tweaking to keep it right. As you can see in the pictures on ULA, the wings are short, and the narrow belt dug into my stomach. With the Gorilla, it seems it will be more lock it in, go, and forgot about it. The shoulder straps on the Ohm, being narrow, also dug in a little bit. Again, while I could get them comfortable for an hour at home, on the trail for longer periods, I'd have to be shifting them more than I foresee with the Gorilla. The wicking mesh plus sitlight pad kept the Gorilla stuck in place on my back more that did just the slick dynema fabric of the Ohm. That the Ohm would slide down my back over time, necesitating a tighter hip belt adjustment, contributed to the discomfort.
The Dynema fabric on the Ohm felt stronger that the 220d nylon of the Gorilla, but not by too much, and I wasn't going to go out and drop them on the ground repeatedly to test that out. Neither of them are as durable as a heavy cordura pack though.
The Ohm could get sweaty in the desert with just the dynema against your back. The 3d wicking mesh of the Gorilla plus the egg-crate surface of the sitlight might be slightly less backsweaty in warm conditions. (also see on the user tips section of the GG website where a user punched holes in the sitlight to allow for more back ventilation)
All the above being said, I really, really, really (I mean, really) wanted to keep both the Ohm and the Gorilla, and use them on alternating trips to see which I liked most, and then sell off the loser for a moderate loss. Financial considerations did not allow me to that. I could certainly see a repurchase of the Ohm in the future though.
Seeing as how they are out of stock on the Gorilla right now, you could order the Ohm, (probably a short wait for that as well), and you could also order the Mariposa Plus, as it is the same design as the Gorilla but less strong fabric and more volume. The MLD prophet will be a wait as well, so I guess it's a wash. That's a frameless pack. There's a recent thread on the G-Spot discussing the benefits of frame vs frameless (as well, somewhere, a Ryan Jordan authored article on the same topic) and the summary of each is that approaching 25lbs, frameless start to get really uncomfortable. Of course, personal experience varies widely.
The Garcia bear can shouldn't be an issue with the Gorilla. That's the can strapped to the top of the pack in the illustrating pictures on their web site.