I use my DRZ for a getaround bike with the RV. The plan was originally to haul it on a hitch carrier. Then my wife decided to give a bike a try, so we haul mine and her XT250 on a small trailer.
Considerations for a hitch carrier should be weight first, in my opinion. The lighter the better on anything except highway miles. I don’t think engine size is a big deal—I have a blast on her XT, though I feel wadded up on it a bit. I mean, I gave it its first 8 or 9 dirt naps before she started beating on it—that’s how much I enjoy that little thing. And even though the DRZ is a relatively small and light dual sport—her bike is more grin-inducing around the neighborhood. It’s just so small and light, you feel like an adult on a kids’ bike, which is always fun.
One time I swapped bikes with a random guy in Arkansas for a 15-mile ride around Byrd’s adventure center near Cass, AR. I declared my love for his TW200, and he fell in love with my DRZ. Which leads me to the point about power.
For a beginner at <45 mph, power shouldn’t be a deciding factor, in my opinion. You want fun and approachable. And relatively light. It doesn’t need to be a motocross bike, but it also doesn’t need to weigh 400 lbs. And since it’s going on a hitch carrier, I personally would want the lightest thing you could easily find used and put a tag on. Plus, on a mountain bike, you have what—1/4 horsepower? So, for double the weight, you need 1/2 horsepower!
So the TW should always be in contention, unless you absolutely can’t fit on it.