Which ever one you choose you will be happy with. They are both great titles, If your looking to get it NIB you better go with MMR since they won't have them in stock for to much longer. I've had my MMR at a location for a little over two years, compared to the others I have this one has the least amount of issues. The issues I do have with it are pretty simple, So I wouldn't worry.

really depends on location: foot traffic, clientele base, hours, smoking etc.
I'd highly suggest you get any and all protectors you can find for the machine. other then that it's all up to you to make sure it's kept up with. in the time I've had my MMR I've probably had to pay a few hundred in upkeep cost. I had to replace 4 coils one time, but it was due to my own ignorance (Don't stick two machines on one timer). Last time I checked the machine was really close if not already payed off. This is with a 50/50 split.

Two year payoff is great for something that can maintain value like a pin. Unlike a golden tee or vending machine which cost 5k and 4k respectively. Then if you go to sell them you loose 50 to 75% not to mention the damn update fees they get you with every year. usually pins hold their value a lot better then that, even a routed well maintained one.