No arguing that the US Valis covers suck something major.
Tonma is a good example of where the differences are slight but I'll like the US cover more because there's less text cluttering up the image. Granted, the Tonma art is pretty stupid no matter what's placed over it, haha.
Now I'm curious how many there are where I actually prefer the US cover. Maybe I'll list 'em:
Aero Blasters
Ballistix
TimeBall
Bomberman (super cheesy and a terrible representation of the game, but still more visually interesting than the extremely simple JP cover)
Cadash
Chase HQ
Cotton
Davis Cup Tennis
Dragon Slayer: The Legend Of Heroes
Dynastic Hero
Forgotten Worlds
Samurai Ghost
Shockman
King of Casino
Klax
Legend Of Hero Tonma
Magical Chase
Legendary Axe
Somer Assault
MotoRoader
Parasol Stars
Air Zonk
Buster Bros.
World Class Baseball
World Sports Competition
Prince of Persia
Raiden
Sherlock Holmes Consulting Detective Vol 1
Shadow of the Beast
Space Harrier
New Adventure Island
Time Cruise
TV Sports Basketball
TV Sports Football
TV Sports Hockey
Vasteel
Ys 1&2
Wow, that's a really long list for someone who usually swears by Japanese covers. There were even some more where I really wanted to go with the US cover, but one badly placed logo prevented me. There are probably some more I could go with, but with both options being so lame, it's hard to decide which has the edge.
That said, my list is dominated by covers where they used the same art on both, just in slightly different ways or with different logos, so I'd say I still overall dislike most of the original, American-made Turbo covers.