If you like a fun, relatively easy game and want your friends and family to play - WCS94
(Plus parts are easier to find with the exception of the ramps)
If you want a game that is hard yet rewarding and had stating power and don't mind short ball times - Shadow
(Unless the diverter assemblies are jacked up or its missing other hard or impossible to find parts)
If this is your first game, I would lean towards recommending WCS94.
That being said, The Shadow is the better game of the two. It just can be kind of evil.
Good luck with your choice. Both are very fun to own.