We spent 11 days between the two places. Even though they are not far in distance, we selected an upscale boutique hotel for our first half of the trip in TI and a larger resort complex in St. Pete Beach for the second half. I have posted the St. Pete Beach portion in that forum.
We stayed at the Treasure Island Beach Resort. This is more of a boutique hotel than a resort, but it was absolutely fabulous. The rooms on line are exactly what you get. The hotel renovations are fairly new and the rooms are just stunning and spacious. We had an oceanfront balcony, full living room, nice kitchen and separate bed/bath. The rates here can be high, but we continually kept checking and found a decent rate.
The beach here is extremely wide, and you can get in your steps just walking back and forth! They do not provide chairs on the beach but they are available to rent. If you are here more than a few days you can buy a chair at CVS rather than pay the high rental fees.
The pool area is not huge, but it is nice and faces the water. During our stay there were not that many children, but I could see during peak times how it could quickly fill up. The restaurant on site provides bar/food service to the pool. The food is very good (with the exception of the nachos, which was processed cheese and chips). We had breakfast almost every day and lunch and happy hour several times. Their eggs benedict were amazing! The burgers are also very good. We would definitely return to this resort!
There are several restaurants and bars within easy walking distance - and a short boardwalk area along the beach. Sloppy Joe's is next door (don't recommend for food, but music and drinks are great). There is a nice, upscale restaurant, Middle Grounds Grill, across the street. Acoustic music in the bar and excellent seafood and steak.
We hit some high-level restaurants, combined with a few dive bars. Kai-Tiki would definitely fit the dive bar. It is about a five minute drive and is across the street from the beach. It was a lot of fun and they had a great blues band. Would definitely return (don't eat here). Caddy's is across the street for Kai-Tiki. We had dinner there one evening and they also have live music. They also show movies on the beach one night. It is typical bar food/seafood type place, but the grouper was excellent and drinks were good.
We did some shopping at John's Pass. Nice to visit, but I wouldn't go out of my way to go there again. Typical beach shops you find in any beachy location. Same with restaurants there - more touristy and overpriced than some of the other local places. We did stop in at Gator's one late afternoon for a great band.
We also went to Maderia Beach. If you are an American Legion member, you shouldn't miss trying the American Legion. It is the number one Legion in the U.S. It is on the water and has fantastic views. We saw a dozen dolphins on the two visits we were there. They generally have both an inside and outside band on the deck. Note: The inside is VERY smoky. The outside allows smoking, but it's not bad. There is also an outdoor bar. Drinks are $3 and the food menu is also really inexpensive.
We went to The Angry Pepper twice, it was that good, once for lunch and once for dinner. It is near the American Legion and has fantastic BBQ (brisket and pulled pork were very good). It is also on the water. It is VERY inexpensive and has a full bar. There is only a small parking lot, so i can be tight at peak times.
We also ate at Shrimpy's Blues Bistro, a small Cajun restaurant in a strip mall in TI. Don't let looks deceive you. The Jambalya is excellent, and so are the beignets. Portions are very large! Prices are very reasonable.
Overall we really enjoyed our trip to TI. We would definitely return here rather than St. Pete Beach area. There was a lot to do and we never made it down to the Dali Museum - but rather just were beach bums for the entire 11 days! Can't wait to return!