With the caveat I don't tow anything any longer, something to consider is if you ever use your truck as a truck instead of as a tractor. A 5th wheel will make using the bed to carry anything much more difficult. A goose neck splits the difference, in that you can flip the ball upside down and have a flush bed floor again. When I had my Super Duty and did tow, that was the route I went. Without an adapter, there's much less selection for goose neck trailers, though. Maybe even less today than was true in the past.
I bought a bigger TT than I really needed and ended up not enjoying it as much as a smaller one. The extra space wasn't worth the loss in versatility and the extra cost associated with pulling more weight to me. Bigger isn't always better, in other words. If I were to get another, I'd likely go with the smallest I could live out of vs the biggest I could afford. YMMV.