Having all three for a long time...it's a real tough call between SM and MB for me. Just a side note...even though SM has the 3 bank target...and 'bouncing green dude' it's NOTHING like AFM (got that one too).
Here's my take on the 3..
SM is a game I go to the basement to play...long(er) ball times and super intense with awesome stacking rules. It's a fairly deep game and it takes a bit to really figure out the rules. The HUGE downside for me with this game is the DMD animation...it blows!
MB is the game in the basement that get played on a whim. Let's say I need my drill from the basement for a project. I'll look over and say..humm...lets give MB a whirl real quick. It's (IMHO) the 'funnest' of the 3 games you listed. It has software your average player can get through. It's kinda nice walking up to a game an knowing you have a illegitimate shot at seeing the wizard mode more than once a year. And for the top players...the 6 MB stack is something I haven't be able to do...or seen done.
ToM is the pretties of the group (barely edging out MB). The flow on this game is incredible. There's a lot of little gizmos on this guy that does make it fun to play (ball save magnet, ramp changing magnet, vanishing ball, trap door, tiger saw mod). The software seems a little tougher to get through than MB but not much. Shooting the trunk may or may not get monotonous after a while
I guess it depends on what kinda of player you are. If you're a hard core pinballer that wants deep rules and a channeling game? Or are you kinda new to the hobby and want a 'fun' game that the wizard mode is generally obtainable?
Here's how I would list them..this list take into account the value of the games also (SM=$5-5500, ToM $4-4500, MB = $7500+)
Newer hobbiest
ToM: Great game to start with... but might get a bit easy for the tops players. Lots of neat 'stuff'
MB: If you can afford it..hell yeah. Pretty much the same description as ToM
SM: Still can't go wrong with this guy
Veteran Pinballer:
SM: Challenging software even for top players
MB: Top players eat this guy up..but there's still the 6 MB stacking that's damn tough to pull off.
ToM: Seems a lot people start with this game. As they become better players it's usually moved out for something different. I still have mine after about 14 years. That should tell ya what kind of player I am