I can appreciate your situation. It's hard to make a choice. From reading your original post it appears you want simplicity that works without a lot of playing with settings.
First let's look at your 2 original choices.
Ace 400-
Cons: 1) For some, hard to see display. 2) NOT waterproof or weatherproof in any way. 3) Some say the Garretts perform poorly concerning unmasking good targets in the presence of iron. 4) Some hate the tones
Pros: 1) Garrett has a good support reputation. 2) You can get aftermarket non-garrett coils to fit it, expanding capabilities. 3) The Ace line has proven to be reliable and long-lived.
Fisher F44-
Cons: 1)We already know that First Texas has shut down "hobby" operations due to COVID-19. That is a negative from a support perspective. 2) Not Waterproof (it is "weatherproof") 3)Users have reported problems with the keypad of certain Fisher and Teknetics detectors.
Pros: 1) Can get aftermarket coils for it. 2)"Weatherproof" meaning it can take a light drizzle without damaging it (I guess) 3)Simple to operate with decent display
Concerning the 2 detectors you mentioned above initially, I'd choose the Ace 400, even though my eyes can't see the display well. I must admit that Garrett is there for the customer, and that means a lot. The Ace line has been around a while, and people continue to find good things with them. Not my cup of tea anymore, but would be a good "beater"
I would like for you to consider what others have mentioned. Namely the Minelab Vanquish 440 and the Simplex + with wireless headphones.
The Vanquish is NOT waterproof. The Simplex is waterproof and includes wireless headphones (must make sure you get that model if that interests you).
Vanquish is multi-frequency where the Simplex is not. Both the 440 and the Simplex can only use the factory available coils, no aftermarket choices currently.
Minelab support once upon a time sucked bad, but is now very good. Nokta, I do not have enough info on, but hear they will take care of the customer also.
Both Vanquish and Simplex are "new" and do not have the years in the field that The F44 and Ace 400 have. Initial Simplex shipments had bad coils, and some others reported issues. Nokta is heavily developing their firmware and supply updates regularly at this point, they are listening. It's mostly enjoyed by those that buy it. It is however a single frequency VLF machine.
The Vanquish I've not heard of any large scale failure or major issues. Multi-frequency like the Equinox, just a wee bit neutered with very simple settings. This simplicity is what makes it attractive to those like yourself, who want to simply get out and hunt with a capable detector.
Best advice is to go to the websites and download manuals. Thumb through them and see which one makes the most sense to you.
My vote considering the pricing range if other detectors were up for consideration??
Vanquish 440 1st choice. Simplex with headphones 2nd choice.
I'd gladly hunt with either. The Simplex offers far more though for your dollar