Honestly I live in one of the rainiest, muddiest places in the Continental US and my Brahmas, pet quality and (near) show quality alike, all do fine in it.
If you get from a hatchery/feedstore you likely won't be disappointed with either, but temperament wise you're likely to enjoy the Brahma more. Some JG's out there are skittish or unfriendly. And of course most just don't meet the truly large size the standard calls for. Same goes for most but not all pet-quality Brahmas. Ours from McMurray are no bigger than the rest of the birds we ordered. But still, very good birds, very friendly, cold hardiness though is as good as most other common/popular chickens. Best to go with the pea combed ones though.