The downside would be that you may not remember to move them to "load" position if you don't have a Dually. I did this a few times even with my DRW and had to lower the TC and fix the problem.
The upsides would be that if you ever do buy a Dually you will be ready. Also if your TC ever needs to be carried on a Dually it will be possible.
Take it from me, a TC is far more stable on a DRW. It's a different driving experience. I loved my truck campers, but it was sometimes a white knuckle ride on my F250. I never felt that way after I bought the F350 DRW.