While there are clearly many pros & cons for each, what always strikes me is how many people you see posting about how they went from a TT to a 5er, and now they won't go back. You rarely (if ever) see posts to the opposite (people who go from a 5er to a TT and won't go back).
While there are some pretty sweet setups with TT hitches, there seem to be more sweet setups with 5ers.
And to be fair, I'm one of those who's had many configurations, and the 5er is my personal preference for larger, heavier trailers. My 38' 5er Toy Hauler tows far better (at approx. 17K lbs) than the 28' TT Toy Hauler I used to have (at approx 10K lbs), both behind the same dually.