I use two almost comically similar lenses: a 60/2.8G macro and a 50/1.4G fast prime.
With such similar focal lengths I choose between them based on the look that I want to have. The fifty is for f/4 and faster, and the sixty takes f/5.6 to f/11. Not that it's a strict division, of course – I just do that when most of the photos are likely to be within that range. Otherwise that would be weird or something.
All of these were taken with the fifty at f/1.4, where the lens is nowhere near its optical prime, but it certainly has its own look. It's fun on film, too.