IMO, thin covers don't mean anything. It doesn't matter if the cover is 1/4" or 1 1/2" thick, the ball will still perform the same if the RG and Diff numbers remain the same in both thickness's of shell, imo.
Thick covers, especially Legends/LaneMaster only limits you as to how dense you can make the core. This means you can't get low RG balls as well as the lighter weight balls being less dynamic than the 16lb. version.
The only bad thing with a thin cover is if the cover was prone to cracking, which I haven't been aware of any problems with this company. =:^D