You will loose some height moving from a fiver to a TT, but probably not gain much advantage on length since a lot of the fifth wheel is over the truck and travel trailers add another three to four feet behind the truck's bumper for the A-frame/tongue. Your wife will still have to negotiate the outside stairs, too. As stated above, I would still invest in a good WD hitch with built-in sway control. Having towed both TTs and fifth wheels with the same truck, you feel crosswinds and semis a lot more with the TT.
Rob