Wow... that’s actually a hard call. I guess I’d say JM... but not by much. They both have a lot of cool things going on and they were actually my first two (working) games. They’re both fun games with kind love it or hate it themes... and they’re both a little flawed.
I guess I’d say JM is a little tougher and a little faster, with the short little U turn ramps. The glove/matrix is a cool toy, and adds some strategy to the game, but maybe it was a little too complex for its own good. There’s a little more scoring potential in the rule set. Music is pretty cool, but the voice calls are almost laughable... although compared to some of the stuff now they’re not bad impersonations.
Dredd has 4 flippers and a little more shot variety. Music is love it or hate it, but the voice calls are cool. The Deadworld/crane is a pretty useless toy, especially as implemented on the original game, but the mod version is sort of neat. Has a pretty basic mode based rule set, although there is some strategy to being able to choose your mode it’s really not that big a deal, IMO. Big long looping shots are always cool to hit. No pops.