I have had my MM and TOTAN restored, and I am having my MB, AFM restored. It will be a very long time, if ever, I will get what I put into them.
So here is what I suggest, pick the pin that is your favorite and that you will never sell unless you absolutely have to. Out of the pins listed, only you can answer what is your personal favorite. I would not have somebody answer that for you.
MM has gone way up in price and I am still way upside down on it even though my base machine cost me 6000.
I do not look at my machines as an investment. I don't think most people realize the cost of labor and parts on a restore is often at least double the base price of a pin, unless it is a cheaper pin then the restore can be almost 3 times the base price. (Think 2300 Whitewater = 7500 restored pin) Too hard to ever "flip" a restored pin. So it is not a good investment, but rather a really fun purchase.