I have done both, so I would say that I prefer the Summit. Why? I felt the food was a lot better in the Main dinning room. The Cabins are very different and I had a C1 on the Summit in the very back of the ship and it was awesome.
I felt the cabin was much nicer. I will say that NCL did stay in Bermuda 3 days that was a plus. Not sure what you are looking at on the Summit but we stopped in Newport, RI a plus for me and Boston for me was a plus also. I felt the Summit was about 2 steps above Dawn and this is just 1 person's opinion.