Well you have owned it already. For me, I really need to be pining for a game to give it another run in my house.
So it comes down to IM and BSD. I own both, and I guess it comes down to my mood. Both are shorter and tougher games. And both have something you are specifically trying to do. On BSD it's all about the Thirty Millions. Stack it up, and watch the points fly. Kill Dracula, or collect Castle Jackpots during it for huge payoff jackpots. It's a blast.
IM is similar in that it's fast and brutal, but it gives you two main objectives. One is a single ball objective (Do or Die hurry up) and the other is through the whole game (Jericho). I tend to try and setup, but not start for the first. The second always feels like a consolation prize. However, once in a great while I'm good enough to have a collect of Do Or Die Hurry Up start Jericho. But that's pretty rare for me.
IM can also bring amazing pinball satisfaction and frustration very quickly. If I have 10 minutes, I can bang out 3 games of IM and be thrilled or angry. But I always seem to be satisfied. IM delivers.
So I guess with all that, I'll vote IM. But I think that's only because BSD has been in my house a long time. If you asked me 5 years ago, I'd have voted BSD because it was a complete addiction for me then.