Why Elmar-C 90/4 when already owning Elmarit-M 2.8/90mm (from 1990s)

Can anyone give me a good reason why I should but a second 90mm lens, El Cheapo from the bland days of Minoltastan? I want one! But does it make any difference? I have a EVF2 for my digital M bodies so not much concerned about focus issues.

It seems the lens you have is better and already pretty small. I don't think it's worth getting the other.

Elmar-C 90/4 is very small. Smaller than https://classic.leica-camera.com/de/Leica-Elmarit-M-90mm-f-2.8-11807/11807SH-3648149​

Sorry for bold font.