Re: 5wt vs 6wt for first rod...
I'll start with a snarky comment first.
Buy the red one.
With that out of the way, here's just an honest opinion.
You will eventually commit to a quiver, so go to a fly shop and test out a few rods. Choose the one that allows you to cast the widest payload range for the type of fishing that you plan on. A good shop employee can walk you through the process.
Fish the snot out of that rig until you feel like committing to a second rig.