5. Five. Definately for learning.
I started on a 4 and if I had it to do over I wouldn't
My instructor incouraged me to get a 5. It's actually easier. You can visualize better how the music is constructed (the changes, the relationships) when you can move across the neck instead of up and down.
Some keys are way nicer to play, notably Eb.
It's also easier to move from 5 to 4 than the opposite.
All that said, after you learn and get comfortable with the instrument you'll probalby own a couple and you may come to prefer 4. Or just love both. But starting out, go for 5.