Worth keeping inning bosses?

SDS

Any reason to keep these 3 bosses other than xp? I easily finished 1st inning and felt like I was grinding for nothing. Seems like selling them might be more productive.

SDS

Lee smith is a keeper. Ive always done good with his cards, with the parallel system this year he should be good for a long time

SDS

Yeah I sort of made a mistake already. I sold Piazza before (for 75K) but then today heard about the collection so I bought him back for 45K and locked him in. I didn't have enough stubs for the other two but figured I could get them ASAP. Now regretting it as I didn't have trouble with 1st inning completion and now wishing I had my 45K stubs back as I'm finding stubs hard to come by.