Fit and finish depend on workmanship not thickness of metal used.

You will not wear through an 18 gauge sink.

The differences are slight when it comes to sound sink produces when struck and possible dings if hit by something like a cast iron pan or dutch oven.

Mine is 18 gauge. It is not loud. It is heavy duty, hard working and IIDSSM pretty dadgum awesome. I don't really think that there is a big difference unless you plan on living in a kitchen that works closer to a small restaurant than a regular home cook's kitchen.