I haven't been disappointed by any of Leroy's work, there are a lot of beat up marbles that can be rejuvenated. Ultimately it's your call. I think there's enough clear glass on that one still that can be enjoyed with all the battle scars, since most of what's going on is close to the surface and not obscured like you'd see if the good stuff was closer to the core like most other handmades from that era.
Imagine the kid on the playground tossing that bad-boy around. I've seen a similar one in Red that's worse off, but could likely still be helped if that's your thing.
Big John shows an excellent example though, and not too many would disagree that it looks a lot better than it did. Unless you're a purist that likes the history (in which case one could argue that you could effectively take a polished marble and pass it on to a new generation for them to play with on the playground and earn it's battle scars all over again). Marbles are toys and no doubt in my mind that even a polished handmade still has it's uniqueness compared to to any run of the mill (ie: current) marbles getting churned out by machines nowadays.