I agree. Nice attention to detail, Stu. ...and kudos for soliciting opinions.
I'm going to preface this by saying that I have no plans to aquire a Skateball (despite loving the PF artwork), but I would also vote for the shortened shooter groove over a new curved one, for a couple reasons:
A) It seems like it would be a nightmare to get that curved groove to be EXACTLY where it needed to be in order to hug that ball around the path of the metal. I would imagine with slight incosistancies in groove curve and ball path you'd end up with the same problem (ball wear, just in a different spot). My guess is that would be avoided with a shorter, straight groove.
B) I can't think of any game that has a curved shooter-groove (would be interested to know if I'm forgetting a title that does). That might be cool to see on a new game, but on a repro playfield where you're trying to replicate a product that is as close to the original (decades old) product as possible...probably not the place to start getting experimental.
Just two more cents for ya, Stu.
Elephant Eater Comics