None, whatsoever. Nobody will ever ask, unless you're applying for a job that flies conventional gear.
It can prove to be an ice breaker when your interview begins with a logbook review, and your logbook has a picture of a unique airplane that you've flown.
A conventional gear endorsement really has no place on your resume, unless you're applying for a conventional gear job, in which case you're expected to know what you're doing, and the endorsement is a formality that you should already have.
I don't have a conventional gear endorsement. Nobody has ever asked if I have one. Or cared.
An endorsement is not a rating.