It was a party of three adults and we all wanted pictures with the characters. The upper level worked out better for us because the characters could get behind my mother and I and we got plenty of pictures without us having to get up (except for Pluto). My friend was on the other side of the table, so he didn't have to get up either. Only time we both got up was for a picture with Mickey.
When we ate on the lower level, my friend (who was stuck in the middle) also needed to go to the bathroom twice, which meant I had to get up to let him out. My friend didn't want pictures with all the characters, but even one means having to get up.
This was just our experience, but I'm not that keen on getting up and down more times than I need to during a meal.