The Holiday Inn is on the same side of the street as the Hilton and is next door. (there is a small pond between them). The Hilton is closest to Downtown Disney (as in directly across the street), and the Holiday Inn is about a 5 min walk.
When we were researching, the Holiday Inn was much cheaper than the Hilton. I also liked that the Holiday Inn had balconies and the Hilton didn't. However the Hilton has extra magic hours which is pretty awesome.
We chose to stay at the Holiday Inn. It's fairly new (open a couple of years now), and is very nice. I liked it, and would stay there again, mainly because of the ideal location. They both share the same bus, and it was always on time (every 30 mins). The rooms were clean, modern (had a mini fridge AND a microwave), and the beds were comfy. I was happy with our choice. We stayed in March 2012.