GG Gorilla pack v.s GG Mariposa plus

I actually have both packs at the moment..

Yes they are very similar. the mariposa is just slightly bigger. the gorilla has 2 bottom side pockets while the Mp has 2 side pockets on one side and a single pack length pocket on the other. The MP also has load lifters which will allow more comfort at higher weights. thats about it other than the slight volume difference:

gor-
3,000 c.i. (46 l.) total
2,400 c.i. (39 l.) in main pack body/extension collar
600 c.i. (6.5 l.) in all pockets combined

MP
4,244 c.i. (69.5 l.) total
2860 c.i. (47 l.) in main pack body/extension collar
1384 c.i. (22 l.) in all 7 pockets combined

I personally will probably keep the Gorilla just because i don't need all the extra pack that the MP provides.
It just comes down to your own gear list, expected use and preference..

"Better weight distribution? More durability?"

ultralight packs carry best if they are completely full. If you opt for the bigger pack and don't fill it, it won't ride as nice.

they are both made of 140d so durability should be comparable.

Thanks Jason, That makes since on the pack being full for comfort. Do you know if you can strap on a bear canister on both packs?

Hmm you could probably get a bear can under the over-the-top closer thing but not sure how well it would hold.. seems like if the main body was full it wouldn't work too well.

I've tried a bear can atop a pack once and didn't like it so never tried it again. It was too top heavy and didn't seem secure now matter how tight I strapped it..
The bear can will usually be your heaviest item so I like it right in the middle of my pack. I do quilt first, the bear can vertical with clothing on the sides and then everything else on top.