Admittedly, I am a fan of the Venetian/Palazzo. I was there for Palazzo's soft opening and had the opportunity to be the first to sit at a few of the Palazzo dealers' tables. The Venetian/Palazzo are my favorite casinos.
As for hotel, Palazzo is the newer of the two so for a fresher, newer hotel, I would suggest staying at the Palazzo. I am not a big fan of staying at Venetian.
As for gambling, Venetian tends to be more fun in my opinion. I like the congested, excitable feel of the Venetian. The Palazzo tends to be more spacious, open, and less exciting.
As for comps, the last couple of years I get the impression the hosts haven't been as generous. I am not sure though since my betting average has tapered down. I still get my fair share of comps for restaurants and tickets, but I don't think I would get that stuff if I stayed there. My suspicion is they would use my comps for room nights and I would be SOL on the amenities. I really don't know anymore I stopped staying there. The hosts always ask me if I am staying there, when I say no, then they calculate how much they can comp me for whatever. I never really had a permanent host here 'cause I can get everything from the host station.
As for decor, I definitely suggest spending time to walk around. I think the architecture is great at the Venetian (I really don't know much about architecture, but it is visually pleasing to me). The atmosphere is relaxing. I am not a big fan of shopping, but the Grand Canal Shoppes area is definitely nice for taking a stroll.
As for the employees, I have never, ever had a problem with any of the employees such as dealers, hosts, and wait staff. They have been great to me ever since I started going there.