Sunrise:
Koh Tao is MORE touristy that Phuket. Yes, it's small and pretty and has lots of cheap places to stay and lots of backpackers, very groovy for hanging out, but there is NOTHING else. There is no real local Thai life there, only tourism. Phuket, on the other hand, was already a well populated island and very rich before tourism arrived. How many small fishing villages and local temples are there on Koh Tao?
main temple on koh tao is at the top of the crossroad just up from the Mae Hadd port aread, you cant miss it!!
ps. what else do you want to do apart from diving anyway?!!
well if you do want to do anything else on koh tao try the following
...
1). rock climbing
2). mountain biking
3). learn to cook thai cuisine
4). learn thai massage
5). check out the best gym Ive seen in thailand
6). hill walking
7). coasteering (that is coming in very shortly)
8). go snorkelling with black tip reef sharks
9). try the several dozen different restaraunts offring cuisine styles from around the world
10). Visit a health spa.
11). then go diving again
hey, I even forgot about chilling on one of a dozen different beaches, catching a movie, going to a bar, going clubbing...
I'll take Sunrise's point though on Phuket, it does get knocked a bit harshly, Phuket town though itself IS in my mind a large overcrowded city. The diving west coast though is excellent. As for bar girls, you will get that anywhere in thailand, it may just be in your face a bit more in phuket than on koh tao, but the industry is everywhere!