Q: Say you have g b d with bass in c. When would you call it G/C as opposed to Csus2maj7
A: call it G/C when you are confident that your reader can understand that. call it Csus2maj7 if you are not confident that your reader can understand G/C. .... If you are confident that your reader can understand both, i'd say you might as well use G/C because it takes way less space on the page