I've stayed at Resort 66 twice, stayed in Via Roma twice and now own at Via Roma.
Resort 66 is a converted motel for sure. I've had the pleasure of exchanging into a one bedroom unit gulf front on the first floor and a one bedroom unit gulf front on the second floor. Other than these two units, I wouldn't consider staying there. You get what you exchange into so you can find out what you have before you confirm. Even with the view, I think there are better options on Anna Maria. Some people like the small resort feel and coziness. The beach was replenished last year so it is wide again. The gulf is incredible but the entire west coast does get hit with red tide sometimes (not just this area but from Tampa on down to Marco Island). Although the location is great, I can't recommend it.
Having stayed at Via Roma, I bought there a couple of years ago. The units are larger than 66, cleaner, and more airy. I own a unit that is last from the beach on the gulf side and still see glimpses of the water from the bedroom windows. Housekeeping brings fresh towels daily and empties garbages. Everyone that works there is friendly and accommodating. There are no planned activities other than your usual welcome breakfast/lunch. The beach is incredible! There are many wonderful restaurants in the area and a free trolley on the island. It is definitely a laid-back place with many things to do within driving distance (we take a day trip to Tampa or to Disney each year as well). Although it doesn't have the luxury of Orlando timeshares, for me it has everything I want... a clean, well-run resort with a killer location on a great beach.
If you get the opportunity to visit 4th of July, it is a huge party for two nights! Everybody brings chairs on the beach and sets off fireworks. There are also big fireworks displays put on by restaurants that you can see up and down the beach. On the weekend, the island has a parade that goes by the resort with the floats hurling beads, toys and candy at the kids. It is a fun way to enjoy the celebration without the hassle of crowds and lines.
BTW, another resort worth checking into is Umbrella Beach Resort. It is also on the island. It isn't gulf front but the units are very large two bedrooms and more luxurious than others. It is a very short walk to the beach (across the street). I have been able to exchange into Umbrella four times over the past few years!