Pinball is funny... I think it's impossible to get just one game under the premise that it will have repeatability. Yeah, some are way deeper than others...wouldn't argue that...BUT, they all can lose their luster to some degree after repeated plays. If you truly only want to own one pin (at a time), I'd look at this first pin as a temporary resident. That means going for a title that will be fairly easy to move when you are ready for your next challenge. BSD is a perfectly good choice for this...it's fun...it's hard as hell...and you'll probably have a good shot at selling it for close to what you paid (give or take a few hundred) assuming you don't over pay.
I'm going to assume, like Shadow_E, that you are in the $1800-$2600 range (adjusting his estimate down a little). Out of the pins that I've owned... I'd say I would look for a Whirlwind or a Johnny Mnemonic... I'd also consider a BSD, but from my experience (having a BSD in my collection) I think I'd go for the other two first.
You're going to field a ton of varied opinions on this matter...a lot of it boils down to personal taste. Luckily, it sounds like you've played quite a bit so you probably have a good idea of what kinds of game layouts you enjoy.
Good luck (and don't forget to factor in buying magnetic hex drivers, a DMM, and a switch adjuster tool...along with various fuses, Novus, paste wax, and a bottle of rubbing alcohol!)