I don't think there is anything in Ubud with a big hotel feel (the Aman, which is probably about the largest, has about 30 suites), but a private villa is always wonderful. I generally prefer to travel that way on vacations. The only negative with a villa in Ubud is that you will likely want a driver standing by all the time in case you want to go into town, whereas the hotels slightly out of town have shuttles or drivers always waiting around, and you can walk everywhere from the accommodations right in town. Drivers are inexpensive though - about $35 a day - so you can just look at it like a car rental.