Need backpack advice?

should i use the gregory palisade 80 or the gregory whitney 95? color doesn't matter, and the palisade and whitney have enough carrying capacity that that doesn't matter either. which is better for 4 season/ appalachian trail/ PCT/ type hiking? i was set on the palisade, but the whitney seems so tempting. it also seems better. i am a resolute person, so please take your time in explaining the benefits or downsides of each.