Hey Dave. "Knowing" you the way I think I do I'm almost willing to bet you'll go for temperament first and the rest is secondary.
If it were me, that's what I'd be doing too. I think that's where your heart of hearts lands. You're a smart guy who puts lots of thought and diligence into your decisions.
I look at it this way...
Male or female? It sounds like you don't "really" have a preference. And when it comes down to it, you grow them out slow and the size difference isn't a deal maker or breaker...
Best looking? Well, let's be honest...they're ALL going to be gorgeous animals, and beauty is in the eye of the beholder. So I don't think you can go wrong any which way.
Best temperament? This is the only variable (IMO) that will truly seperate one from the pack.
In 5 years you'll be happy you picked the "sweetheart" of the group. You won't be thinking "this snake is so sweet, I love him/her so much, but that other one was a tiny bit prettier".
I guess my point is, with looks the difference is miniscule... With gender the difference is subtle especially grown out over years...
While temperament can be worked with, isn't their personality what truly makes us love the animals?
Anyway, I don't think you can go wrong any which way. But my gut tells me you'll go for temperament.
Good luck, I'll be excited to see what you choose!!!