Ohh boy, that question is not an easy one to answer. Everyone will have a different opinion on which is better and why. In the end it will come down to what best suits your needs.
My .02 is that if you are looking at larger trailers, a 5th wheel might be the way to go. When trailers get heavy, 5th wheels tend to tow better because of how they place all the weight directly over the rear axle instead of hanging off the back of the truck. They also tend to have a lot more exterior and interior storage than a typical travel trailer.
The downside is that 5th wheels are typically more expensive than a TT of similar length. You probably wont find a 30 foot mid-level 5th wheel starting at $25k like some TTs.
This is really only a small fraction of the pros and cons of the TT vs. 5th wheel debate.