I'm a big fan of Art Deco, and see that the MGM Grand has Art Deco styled petite suites, which price-wise are still cheaper than the standard rooms at the Venetian and Belligio. Any advice on wheather it would be better to spend the extra money on the Venetian or Belligio? Also if Belligio, is the lakeside room worth the extra cost. On all of the above, I'm really looking at value here more than cost (I don't mind spending the extra money if it is worth it).

Depends on how much of an art deco fanatic you are. Of course, the rooms at MGM are not going to be on a par with those on South Beach in Miami, but if that's your thing, go for it.
The rooms at 'BELLAGIO' and Venetian are standard traditional upscale. Crown moldings, muted colors, nice carpetings and curtains, marble baths, etc. They're considerably nicer than the MGM's standard rooms.
My biggest gripe with MGM is that it is so inconvenient to use the hotel. Rooms can be 20+ minutes walk from the entrance, lines are long to check in+out, and the casino has gotten very mediocre and mainstream in appearance and ambience. Feels a lot more like a typical Harrah's than during its early glory years. That's because the MGM now competes for a much more middle of the road clientele, no longer the upscale gamblers.

Bellagio. GO! Go! GO!! Absolutely breathtaking. Request a lakeview room!

I have not stayed at the Bellagio..although I have been there a few times..I have stayed at the Venetian several times...I just stayed at the MGM last week...Arguably most people will say that either of these are better than the MGM..but I was upgraded to a suite at the MGM and the room was very nice..that said, the rooms at the Venetian are extremely nice also...Actually when it get down to it..there is plenty to do at any of these hotels..and in the final analysis I am not sure there is a big difference between any of these hotels...I do not necessarily argree with the previous poster in regarding check in and out lines at the MGM..in fact I have had more problems with this at the Venetian..It is not a 20 minute walk to the rooms...That said, it is a very large facility, and it does take some time to walk to some of the restraunts or pools. I would stay where you can get the best price ...cuz I do not think there is THAT much difference....

Definitely Bellagio-stayed there last Feb. with a friend and were upgrade to a lakeview room to see and hear the Dancing Waters--it is gorgeous at night--hotel staff is fabulous-went out of their way to help--ALL requests were done-called before arrival for resv,to Le Cirque Rest.and told sold out--walked up to concierge and gave my hotel key and got table for 8 with no problem--make sure you see the art exhibit in house--best private collection outside of Lourve---but please also go to the Venetian to see the painted ceiling and to shop in st.Marks sq--conplete with gondoliers and people in Venice Carnival costumes--but don't eat at the Italian rest.overlooking the Grand Canal in the Venetian--overpriced with terrible service.....Howewver,Le Cirque was to die for!!!!!!!!!!!!!!!!!!!!!!! and the interiors of the rest.were fab-service was impeccable.