North Face, Kelty, REI?--seeking friendly advice!

* i know many of you have extensive experience using/buying backpacks.
Please lend your advice!

After hrs of internet searching for a internal frame backpack (a
versatile and reliable pack to be used down the road for various month
long, intl., backpacking trips), 4,000-5000 cubic inches, top AND
side/front entry, and preferrable detachable daypack, ive narrowed down
the following candidates and am now seeking your advice. The backpacks
listed below all meet my standards, but i have nothing to judge comfort
and brand reliability on. i'm currently volunteering in South America
and therefore have to depend on internet shopping and wonderful people
like you offering feedback. Which should i go with?! ALL advice
very appreciated!

1.) Kelty Women's Red Cloud 5000 Internal Frame Pack
2.) The North Face Women's Crestone 60 Internal Frame Pack
3.) REI Venus Pack '06