Eric,
Welcome to TT.
The first place I would go for good advice is Randy at Cut N Shoot Customs, AKA Papa Zook, the owner of this forum.
As for basic information...... regardless of which bike you choose; I would plan on spending the money for a custom seat that fits you and your passenger. I have never found an OEM seat that gives all day comfort regardless of bike. Towing capacity should be kept to around 400 pounds. Most motorcycle trailers come in at about 250 lbs (or less) empty so you will want to limit your cargo to about 150 pounds. I have an auxiliary fuel tank giving me a range of a little over 300 miles. It is a feature that I'm glad to have. I recommend it. I'm also a fan of independent rear suspension and think having a rake kit, or easy steer, is a must.
Just a few thoughts to get you started. Good luck..... Jim