[at-l] Which backpack?

[tomman@attbi.com (Tom Mantooth)]

I am trying to decide which type of backpack to use, the Internal or
External frame.  I like everything I have read about the internal frame
but I sweat a lot in the heat, like I look like I have been in a
shower.  I am afraid that the sweat will be enough to soak into the
backpack with a internal frame and get the contents inside wet.  It may
also cause me to get heat rash.

Still I feel the internal will carry more comfortable on the trail.  I
also worry about the external frame catching on tree limbs and brush.  I
also worry that it could cause me to have balance problems in some
areas.

I hope to be able to rent each here for local hikes to see which seems
best for me, still that is nothing like the AT.  I know that in the end
I must make my own decision but would like some feedback from the group.

Thanks,
Tom