[overdriver]

Are you talking about the difference in the open coil pick ups that come on the Classic LP model, & the pickups covered that are on the standard , standard plus etc.??? The open coil pups on the classic some say are the same as the standard sans cover. I have both a classic and standard plus lp , the open coil use the same Alnico V magnet same wire.They have a different designation on the bottom and a bit different peel off sticker on them when new. They are a bit nosier because of the lack of a cover around lights etc. they sound hotter and a little clearer the bridge pup is hotter than the ones on the standards. They do sound a litte different ,better???

Degrading the tone?, well depends on what tone you are after.
Alot of people like the open coil pups, I think they work just fine ,as I do think the covered. I changed the ones on my classic for Seymour Duncans (open coil)not a whole lot of sonic diff.( I perfer covered)
IMO a better upgraded Would be covered pups made by someone other than Epi. , with good german sliver covers. But hey if you have a line on the open coil Epis cheap try em. They sell cheap cheap on e-bay etc.