I own both. They're very different games.
TS is much more challenging with harder shots. Consequently, more rewarding when you do well.
JD is the ultimate mode game - 4 flippers, 4 ramps, endless shots, tons of modes, supergame, widebody.
Both have great art packages, JD certainly has better music and callouts.
I always have a blast with JD and 1/3 times I walk away from Shadow frustrated.
If I had to pick it'd definitely be JD.