As noted above, there are pros and cons with both. With a properly set up TT you should not have any sway, so that's not a deal breaker either way. The 5ers have a few advantages including the bigger storage bays. They tow nice due to the wheels being set further back.
The "con" is that you generally need a bigger truck due to the much greater pin weight, and 5ers generally cost more. TTs are kind of more "bang for the buck" IMO, but I'd love to have a big 5er with a big 1 ton truck. Not in this year's budget though.