Spad fan here, although I’ve never tried AAO extensively so I can’t do a direct comparison. Both seem to have avid fans and once you’ve committed to either of these and have used it to program your hardware, you obviously tend to stick with it. Whichever you pick, you can’t go wrong. Once you start using them, you’ll find there’s absolutely no need to map anything in the in-game controller settings, perhaps only camera views but nothing else. After a couple of years of using Spad, I get the goosebumps whenever someone mentions that he can’t figure out how to bind something using (gasp, yikes) in-game controller options. I’ve even forgotten what these look like.
Spad is the more expensive choice, because with MSFS you absolutely need to use the beta channel to get all the latest updates therefore you need to have an active license to get those updates (which come very frequently, almost on a weekly basis). Which means depending on your hardware (e.g. if you want Elgato Stream Deck support) you may end up buying the complete license (90 EUR). Then a year later you need to start paying 15 EUR more to update your subscription on a yearly basis. There are plans for 2-3 years or lifetime.
Is it worth it? Absolutely. Once you start using it, you can never go back and the money investment seems a trivial thing.
Does it have the best UI out there? Absolutely.
My main gripe is its severe lack of documentation. It seems that once they decided to suspend the forums and migrate to Discord, the limited documentation and examples that used to live in the forums simply froze in time. Nowadays the only way to get some decent examples is to either ask in their Discord and hope someone answers (the creator usually does) or watch the various tutorial videos in Youtube. These will mostly give UI-related examples, most of which you could have figured out by yourself with some trial and error.
However once you start digging for more complicated stuff, like how to build non-trivial regular expressions, how to use certain and seemingly undocumented features of spad etc, you will find out there’s virtually zero documentation or examples. I think this is where AAO shines. Even in the UI, I’ve found options that I’ve no idea what they’re doing or how they’re actually supposed to be used and no one seems to have ever asked about these in the official Discord channel.
Other than that, Spad is amazing and well worth its money. Judging by the info you gave on your background, Spad might just be ideal for you if money is not an issue.
ps: I don’t generally use ready snippets, as I like to program everything on my own and so far I’ve managed just fine. Perhaps I might just look at a few to see different approaches to achieve the same result.
I need to get back to publishing and setting things up for use!
If not half, then at least 1/3 of the technical questions I’ve asked in their Discord are answered either vaguely or sometimes inaccurately or whatever, even by the most experienced of the users there.