I have Family Tree Maker 2019, Ancestral Quest 16 & Legacy 9 on Windows 10.
My "favorite" program tends to move back and forth between the Ancestral
Quest and Legacy, but I've owned and used Legacy the longest and mostly
prefer it. I especially like the way it handles sources.
I also like the way Legacy interfaces with FamilySearch. The other two
programs also interact with FamilySearch to varying degrees, but I
prefer Legacy's implementation.
There is probably some bias there too. Since, like I said, I've used
Legacy for a very long time.
To be honest, the ONLY reason I use Family Tree Maker is for it's
ability to update trees on Ancestry. Other than that, I think the
program is a train-wreck and it's super SLOW. (Oh, I did think of one
other thing I like about FTM. It downloads high quality images of the
sources to your hard drive when they're available.)
Ancestral Quest is nice. I'm just not a fan of some of their UI choices.
While it's feature set is nice, I think it's ugly. It is decended from
PAF and it shows. While that's a good thing to old PAF users, I
personally don't care for it that much.
Also, as somebody else has pointed out, you could download the free
versions of Legacy or Ancestral Quest (and others) and try them out for
yourself to see which one you prefer.
That's what it really all boils down to... Which one do YOU find most
comfortable to work with.
Todd