We just got back from a trip to Vegas a couple weeks ago. It was our first time out there and we wanted to stay in the middle of the Strip so we wouldn't have to bother with a rental car during our stay. We chose to stay at the Mirage for a few nights and the Bellagio for a couple nights. We loved them both.
The Bellagio was very nice. Obviously it's a beautiful and very luxurious hotel. The employees were very nice and so were most of the clientele. But being ONLY an upper-middle class type I felt a bit out of place at times while staying there as it was obvious a lot of the people staying there were not just wealthy, but flat out stinking rich (people easily worth 7-figures+.) But it wasn't too bad really as there were others like ourselves who could afford to stay there, but simply couldn't afford the lavish lifestyle some of the rich folks were obviously living. The Venetian exudes a similarly high brow air, but is a bit more approchable IMO. For instance when you look at the shops in the Bellagio it's all the name brands that only the EXTREMELY fashion conscious or super rich would shop at. But the shops in the Venetian, while upscale, actually had quite a few stores I could afford to walk into without feeling uncomfortable.
The best thing about the Bellagio is its location. Right in the heart of the Strip. As I already said, I didn't want to mess with a rental car on my vacation (that's part of what I want to get away from while on vacation.) So being in the middle of everything means you can easily walk to most of the major casinos unlike if you were at one of the casinos on the periphery like Circus Circus, Stratosphere, Mandalay Bay, etc. One ironic thing I noticed about the Bellagio was that it was surprisingly affordable to gamble there. We saw far more $5 tables at the Bellagio than we ever saw while at the Mirage. They didn't have as many $0.25 slots though.
I personally think the Bellagio buffet is overrated. Yes, it was good. But I personally found the food at the Village Buffet at the Paris right across the street to be better and slightly less expensive (it's about $20/person.) We were going to do the Aladdin buffet, but ran out of time.
Personally, whenever I get to go back to Vegas I'd like to stay at the Mirage again and definitely want to try Caesars. The Mirage was also one of the more upscale places on the Strip, but a better match for my personality type with its more casual, tropical style. Caesars seemed to have a similar upscale, yet fun feel to it and I've heard their Palace Tower rooms are very pimpy. The Bellagio's main theme just feels like 'look how fancy this place is.' Our room at the Mirage was actually VERY similar and comprable to our room at the Bellagio. The Bellagio room was actually a bit smaller, but had a much larger bathroom. Both had tile all over the place. The bed at the Bellagio was definitely more comfortable and top notch. For those who say you don't spend much time in your room anyway, I'm sorry. Personally my wife dragged me up to our rooms several times during the course of our evenings with all the gambling and free drinks and I'm glad she did. She probably wouldn't have been as inclined to do so if we'd been staying at a more run down place. But most of the major hotels on the Strip have fairly nice rooms. We just got some fairly good deals at both places so why not stay at some of the best for a little more. It's not like I get to go on vacation often or anything.
A few poorly stitched panorama photos of the rooms at the Bellagio and Mirage