Pics are a huge help but I bet the woman's bike could be a real pain for a first build, I'd recommend the mountain bike for the ease of build, the good brakes, and the fit you mentioned.
A first build is always a learning experience
Why not save the bike you like better for the next? That'll give you time to do it up right.
O'course it's up to you - but I built my bike with the "prototype" idea in mind and I'm glad I did. Much as I love it, it mostly showed me what to do differently next time
and there will be a "next" lol - it's an addiction