Aquatic Critter and Emerald Bay are both great, but different. I like going to both for different reasons.
AC is large and has a great selection of FW, SW and corals, they also have a reptile room. They have some wonderful display tanks, and the people there are knowledgeable and helpful. I have been a customer for about 20 years, and since I don't have a RODI unit, and live 5 minutes away, I am in there multiple times a week. I primarily buy my fish from them.
Emerald Bay is a 30-40 minute drive for me, but it's worth it as well. These guys are also very friendly and knowledgeable. They don't have as much square footage (overhead) as AC, and they are saltwater and reptile only. I love going here because I can get a better deal on smaller frags. The other bonus is the owner's mother (I think) owns a curio/knick-knack/thrift store type of shop on the premises and that's fun to walk through as well.
Both are great. Both have strengths and weaknesses. I visit the one nearby and also make the trek to the one 30 minutes away. If my locations were reversed, I could see myself doing the same thing.
Hope that helps.