It might be good to go somewhere and check these out "in-person"
Also - try to look at the manuals and see what is involved in getting from one type of sewing to another.
Does the air-threading include the needle threads? or some kind of needle threader?
Will you need to change the needles to achieve different results?
Will you have to rethread the whole machine to get different results?
If so, how will you do that?
I have a 5-thread Singer 14T968DC which is "easy" to thread compared to my other machines - AFTER i finally understood the threading diagrams. I got stuck on an "easy" part because I did not "get" the illustration.
However, to go from a two-stitch chain stitch to a five-thread cover lock requires rethreading - on that machine, anyway. Don't know about the others.
Might want to check that out. Maybe you just push buttons now to change ?????
Also - check to see what they have for training/help/manuals with any particular machine.
You might consider keeping the Bernina for one purpose - if it does a great rolled hem, for example - leave it set up for that. USUALLY one can change the threads by tying the new thread on and pulling it through - until you get to the needle(s).
Then set up the new one(s) with a whatever you like and leave them that way. Then you can just sit down and do whatever.
I can do the actual rethreading of the Singer in about five minutes now - that does not include the look-up time for the how-to - because I haven't used it enough to remember the how-to yet.