Actually either one, BA or SCC would work very well for you, Scuba Club is more of an all-inclusive "resort", behind those stucco walls and wood gates. The food there is supposed to be very good and like most places the staff treat you like family.
Blue Angel's new owners, Eva and Robert, along with many nice improvements to the property it's self, have added breakfast and lunch, on diving days, to the hotel/dive packages, so it is almost become AI, of AI LITE if you will, (I'm still hoping they will consider making the food thing an option when booking, but that's just me), they leave dinner up to you, you can either eat at the hotel which is now serving dinner with a set menu each night or go to town and enjoy one of the MANY great restaruants of Cozumel.
Have never stayed at SCC, but the rooms at BA are large, with fridges, safes and nice sized balconies with drying racks to hang equipment on. Some rooms have new A/C units and the rest of the property is being upgraded as well. The dive shop has lockers, (bring your own lock), rinse bath, outdoor shower, haning racks for drying equipment and if for some reason you forget to take your stuff down, the guys at the shop do a good job of storing it for you so it won't "walk off".
Blue Angel is probably the more economical of the 2 for up front price, but again, dinner and breakfast and lunch on non-dive days are not included in the price.
Both are easily within walking distance of downtown. Scuba club is the closer of the 2, just about a 1/4-1/3 of a mile out of town where Blue Angel is closer to a full mile, but we walk it quite often. Cabs from either one of them should be very reasonable, it is $4 from Blue Angel to the downtown Plaza (square).
Can't speak for SCC's dive op, although folks that use them seem to be pleased with them. I've been diving with Blue Angel for 4-5 years now and have no reason to move on to someone else, although one of these years we are going to budget some extra money for a day or two of "pampered" diving with Christi and BlueXTSea.
Both are know for having good shore diving, although Coz is not know for it's shore diving, both areas have great reputations for finding lots of critters, mostly juvies, but with some searching you can find a lot of them. Actually the entire stretch from the International Pier all the way north to Scuba Club is where most of the "good" shore diving is on the island.
Villablanca would also be a good choice, it is just a short distance further than BA and will offer the same shore diving opportunities and again not be too far out of town.
