I did a search and can't find this exact topic. Basic question: in Las Vegas, which is the better hotel, the Bellagio or the Venetian?

I'm looking for a nice, romantic spot for a weekend for two. I'll book through AMEX Fine Hotels, so I'll get an upgrade, breakfast, and late check-out at either property.

Main priorities:
-quality of room
-excellent service
-decor/atmosphere

Your thoughts are much appreciated!