I have never stayed in a first floor villa, but I do have some thoughts. If you are on the "bus side" of VWL, especially if you are near the elevators, you will hear the foot traffic on the walkway between VWL and the main resort lobby. You will especially hear the wheeled luggage being rolled along as people show up for their first/last day dragging the luggage over the uneven boards of the walk way. I would think that would be the noisiest area for a first floor room. The "lake side" villas would be quieter, but during the day you would have the pool noise.
Personally, I wouldn't worry about making an upper floor request. It will be quieter (on either side) and the resort is so small that even if you are farthest away from the elevators you really aren't that far away. Look at the map on page one of this thread and you'll see that you are never more than 15-20 villas away from the elevators. That is a remarkably short distance compared to most
DVC resorts.
As for the size of the balcony, I'd say it is pretty close to the same size as the first floor patio areas outside the doors. So I wouldn't make that much of a consideration.
I hope you have a great trip!