I am in the middle of a similar training program (in two weeks I peak at 65 miles a week and I am aiming for a time trial on January 2).
I think a lot of this boils down to personal preference, as evidenced by the fact that folks can't even seem to agree as to whether or not the Alphafly is an upgrade over the Vaporfly. If it makes you feel any better, I think this actually is a "there are too many good options" problem and I don't think there is a "wrong" choice.
I have only run in the Nike Vaporfly 4% Flynknit and I cannot say enough good things about the shoe. I raced a pretty remarkable 45 minute PR in the marathon and while most of that was due to better training (and having a slow record to begin with), the shoe definitely helped.
My 4%s are only just beginning to show serious wear (maybe 300 miles at this point - I very rarely use them for training) and I am picking up a pair of Saucony Endorphin Pro's from my local running shop next week or so. I am excited to try these out because I have been training in (and very much enjoying) the Saucony Endorphin Shift. The Pro also comes in about $50 cheaper than the current Vaporfly (and $75 cheaper than the Alphafly), so I think I will be a little more open to using the Pro's for training as opposed to keeping them in a vault until race day.
There's plenty of good competition out there though and
Running Warehouse has an article with some thoughts on some of the others. I have heard good comments on the NB Fuel Cell as a training shoe as well as the ASICS MetaRacer (which apparently has fantastic grip).