Everything else being equal, a fifth wheel should tow better.  Having said that, I would never trade my 34' silver Avion for a fifth wheel because I don't want to give up the truck bed.  I take at least one quad with me and I don't want to pull two trailers.  The Avion pulls so nice that usually I don't even know that it is back there except for pulling long hills.  I have pulled that trailer across the country several times and I have never had a sway issue or any ill handling characteristics.  I use a quality WDH but I don't use the sway bars.  I've never had the need for them.
Which one is best?  There is no "correct" answer.  It all depends on what the user wants.
I recently put my Avion C-11 on a trailer made to take a quad so that I could put one quad in the back of the truck and the other on the trailer.  It is kind of a red neck toy hauler, but I can take it back off road quite a way without getting hung up on a rough road.  My 34' Avion would never get anywhere near as far back as I want to go.  That is why I no longer use it.