You two can correct me if I'm wrong, but they way I understood it is that external frame packs are better on the trails, and internal frame packs better off trail. If that's true, than you'll want one for the type of hiking you'll be doing most.

I have a small "Peak" internal frame pack that I use for long day hikes. It is more comfortable off trail and it tends to get caught up less in branches and brush, but it's smaller with lighter loads than my external frame pack that I use for longer ventures into the forests so I can't really compare them.

The people I know that use newer, larger, internal frame packs say they like them a lot.

phat has it right too. Tinker with your gear and gear list to lighten your load first. Then get a lighter pack to fit it. (I still haven't done the latter

I have to add this too, after reading some recent posts here about people doing several nights out of a day pack, I think I'd like to try and see if I can fit an overnighter into my smaller pack and work from there. I was really inspired reading about that. I seldom go out for more than 3 nights and I think I have everything I really need to pull it off.