What to consider... first and foremost, buy what YOU like!
Here is the first thing that popped into my head, why are you limited to these machines? Is this what you see right now and you want to buy one right now?
Other things to consider....
Price point is key to a lot of machines. If its a nice original its going to be more then a fixer upper. You are better off posting pictures and prices for opinions to see if it is more unreasonable then asking for prices to pay. Its a little easier getting assistance that way because condition is key because......
Do you plan to restore these? If not, get the best condition one you can find and spend a couple of extra dollars up front. Be patient. You could put more money into it then its worth pretty quickly on most of these models just to get it going (or even worse if you go for the full Monty restoration job.)
The select-o-matic is a great machine, but not for huge money. I picked up a perfect working light up version of the 102 in basically mint condition one for $100 that was on CL for 6 months and they basically wanted it gone. (It was my foot in the door to see what else they had which led to actual artifacts from Paul Revere.... Really, the guy in the poem, you won't believe me anyway so I'll stop there) I figured it would be a good one for a garage machine. It has the can conversion in it and my wife likes it the best of all of my machines
(side note, I dropped it on its face moving it....
Didn't break the glass, just messed up the chrome trim.... Make sure you use straps on your dolly if they are there!)
If you're not planning to become an addict like us, do your research and see what you like, then find that one. You will be happier that way and save yourself the regret of not waiting for "the one"