IMO, definitely Palazzo: more intimate casino property, a bit more contemporary in furnishing, and a great (and conveniently located) concierge lounge on the 23rd floor.

Since the Canyon Ranch Spas connect from Venetian to Palazzo, you basically have access to all the facilities (such as the rock climbing wall) from either property.

I haven't spent much time @ the pools at either property, so that might be an issue, but someone with first hand knowledge would have to speak to that topic.

I find there is probably very little that would tilt things in favor of Venetian. Maybe an upgrade to a Renaissance Suite @ Venetian, but other than that, I'd much prefer to be @ Palazzo.