Which scallops are best to buy?

I'm looking to purchase some scallops for a special dinner and I'm wondering, which scallops are the best to buy? Are there certain types or grades that are more desirable than others? I'm interested in learning about the differences in flavor, texture, and price between the various options available. Additionally, I'd like to know if there are any tips or tricks for selecting the freshest scallops at the store. Could you please provide some guidance on this matter?