When I purchased my current TT, I was torn between 5er and TT. I thought I wanted a 5er, primarily based on living space (more spacious, higher ceilings), and then when I started looking at Pin weight and it's impacts to cargo capacity vice TT and it's impacts, it was increasingly harder for me to find a 5er that I liked, with the layout I wanted, that fit my cargo capacity.
Then, on top of that, there is the price point. 5ers I looked at were significantly higher than TT's I was looking at.
In the end, I went with the TT in my sig. Rationale (not necessarily in this order).
1. Very similar layout/floor plan, close to same space.
2. Significantly lower cost (as in over 10k)
3. Impact on cargo capacity
4. Impact to truck bed space.
5. Added steps to get into bedroom area (wife has bad knees). That was her #1 rationale for the TT we picked.
For a first time owner, I highly recommend you stick to TT's. If you are like the thousands of other owners, you will upgrade at some point in the future. Wait until you figure out, based on your personal experience, what you want in your final RV (if there is ever a final).
Mike