Get the thickest gauge ( lower number ) also check the stainless purity . Some cheap stainless will still make light rust stains , pay a bit more and don't suffer for years with a substandard sink .

Consumer Reports on newstands now reports they found no appreciable difference in performance (including noise and denting) between 23 to 18 guage sinks from various manufacturers (CP does not recommend one manufacturer over another). Type of stainless is important but it is composition not purity to watch out for (I believe it is the amount of nickel and chromium that makes stainless more resistant to corrosion). Type 304 is the most common but I have read that type 302 is better. Watch for the finish, mirror finishes do not tend to age as well as brushed ones.

Get the best guage you can for your price range but don't pay more for a lower guage. I would probably not go for anything that wasn't 304 or 302.