My disclosures: I currently own ST Pro (have played STLE as we've had it on route in the area) and JP, and have route experience with SM (original only, I've played the VE version once at a show and that's it).
So, thoughts:
Nutshell: I think all three are fun games, so in my opinion none of these are bad decisions. They do all play different (whether you'd want SM and ST together I think comes down to whether you want games with significantly different layouts or not, but the rules are quite different so they do not play like the same game).
ST: My favorite. I like flow games, and I think it feels the most flow of them all. The wamp ramp is a valuable and enjoyable shot. There are 18 modes to work with, and there is a lot of strategic value in deciding how to approach it (do you do each level 1 mission and go for KM right off? Maybe go three deep on a mission first to lock in that benefit?). Overall a great call-out package (except for Khannnnnnnnnn, that one is terrible). Negatives would be the art is so-so to bad, the modes can feel sort of same-y ("chase the lights" syndrome), and it can play sort of long on factory set-up.
Having time on the LE, I can say the visual upgrade with the light-show is impressive on the Prem/LE versions. However, given there's next to no gameplay difference (left-scoop feed is different and the left outlane kick-back... that's all I can think of) I'd save the money and get a Pro.
SM: Layout obviously similar to ST, but the rules are quite different. I actually prefer the call-outs on SM over ST. While I have played SM a number of times, I have far less overall time on it. On factory set-up it can have incredibly long (in my view overly long) ball times, but most of my time has been on a version without a center post. I still think it plays longer than ST with just that modification, so evaluate if you want a long or a short player. I don't really view the rules as better or worse than ST, just different (but they do feel more different than ST, so it comes down to the style you like). Art package is bad (other than VE, but you've ruled that out), but I don't care much about art so I wouldn't let that stop you.
JP: Far more simplistic than ST or SM, but I think it is an excellent game for its era. Note, all this is with the ChadH code package installed, it really makes that big of a difference (no more "free" Tri-Ball on ball #3, randomized mode start, and a number of scoring adjustments to provide better balance). It's commonly called a poor man's Addams Family mainly because the rules for the modes are like that game. Shortest player of all three of these with a factory set-up. One ramp but diverter lets it feed to either lower flipper, good shaker use, and the modes feel quite different in terms of what you have to shoot for. I have six games, JP always catches the most eyes of anything I have ever owned and is what most new people want to play.