I've had both and ended up going back to a TT for some of the reasons you mention. Mainly, I like having the bed of my truck open for bikes and stuff. Also, not having to clear it every time I want to hook up the trailer is a huge plus.
As for towing, the 5th does do better but with modern anti-way technology and having a big truck as you do, the difference is not that noticeable.
As for usability of the actual trailer I did like the 5th better with the bedroom being so separate from the other parts of the trailer. Again though, not a deal killer.
I agree with the previous poster that said start small (cheap) in case you want to jump ship. Also, REALLY look at the floor plans to decide what YOU want. I made the mistake of buying the first trailer that I fell in love with when I didn't have much experience and ended up with a floor plan I really didn't like.