To clarify a little better, of all your lenses, which --one-- lens is your favorite, if you had to pick a favorite of the three or four that you own?

The 50mm prime without hesitation, it is the most versatile and all round prime lens, yes it has limitations, L or no L it out performs just about any lens, (of course the 50mm f1.2 or f1.0 would be a perfect world choice but at a much greater cost) even the humble 50mm f1.8 is a very good lens and very good value for money.

Prime lenses by their very nature are optically superior to their zoom counterparts.

Limitations (cons)

Not much good for wildlife (unless you have a cloaking device lol) and no good for wide angle, you also loose perspective. Its not a zoom so you have to do the leg work instead of zooming in/out. (Also a pro as it helps you learn composition the old fashioned way)

What it is good for (pros)

Excellent optical quality, excellent in low light, can be used as a macro with the addition of extension tubes 1:1 can be achieved with the right combination.

Minimal distortion, extremely sharp, especially from f5.6-f11, very light and compact.

Canon/Nikon/Sigma, doesn’t matter they are all on a par optically and performance wise.

A good proportion of what I shoot can be achieved with a 50mm prime.

I think that answers your question from my point of view. I suspect that few will disagree with what I have said, except the exclusive wildlife/wide angle shooters.

They wouldn’t have made the cane if you weren’t meant to break the rules