If you posted this on the Bali forum you would find 98% for Bali.
Have been to Bali and Phuket many times. I find that in their own way both are pretty good. Beaches are better in Phuket. Surf beaches are better in Bali. Quality of goods are better in Phuket.
I think a good hotel in Bali is more expensive. Eating out might be cheaper in Bali. Taxis are half the price in Bali compared to Phuket.