TRI-ELMAR-M ASPH. f/4/28-35-50 mm

Currently I have a M6 with 28mm Elmarit-M

When I move to 8x10 Large Format, I'd still like a system for street photography. I was thinking of selling the 28mm and getting the tri-elmar.
I'm curious to know if anyone here has experience with this lens. How far off is the quality from the fixed lenses?