Midship near the elevator is a great location. That's where I always try to book. I ended up with a cabin between the midship and the forward elevators, which is not ideal from my perspective, but I'll take it for the price! The regular balconies on the Summit are adequate.
There are 4 CC cabins on deck 6 which are a tad larger and have larger balconies: 6143, 6144, 6135, and 6136, although the last two are connecting staterooms.