@Tj, I use supernova mostly for the same reason most people use their software, I have used it for 18 years, am very used to the way it works and find that I can do a lot with it. I did try jaws but found it's settings and processes literally incomprehensible, I couldn't set it to do convenient things like stop reading capitals when on continuous read, I also didn't like the web page reformatting it did.
Supernova is extremely easy to monkey with the settings of, which is helpful.
What I like particularly about supernova is it's ability to have a useful virtual curser and work well with pretty much anything that has text, whetherh or not it is particularly mapped to do so, which makes it very handy for playing games like the SMugglers series, since the virtual curser in Supernova is highly useful and very easy to move around the screen and perform mouse operations with, it also works well with console windows and interactive fiction games. Another advantage of supernova is an instant flick off of the hotkeys and/or voice, none of that key grabbing or putting to sleep thing that Jaws has, meaning that frequently I'll play a game, watch a film or do something else I don't need my screen reading program for, pause it, alt tab out of the window ad go and answer my email or write on this site or similar, then just alt tab back, flick off the hotkeys and/or voice and continue.
I also like the human Orphius voice Alan which can be used with Supernova. The synthetic dave voice is pretty grotty, and I personally really! do not liek eloquence (it's Uk english accent is very irritating), but I find the human voice a nice compromise between speed of reaction and understandability, plus because I have realspeak daniel for both Sapi and for my phone, I would rather not have it for supernova as well.
I have tried Window eyes on my lady's computer, but I'm afraid I didn't get on well with that at all, I found the inability to read windows and a lot of the virtual curser commands a right pain, also setting it was a nightmare, particularly since it often wouldn't read very basic windows elements like screen alerts, meaning that if a window popped up saying "Do you want to delete the entire contents of your harddrive" you coulldn't read anything but the okay button. It was also extremely bad at starting and generally rather buggy, though I don't know how much of that was my lady's computer since that was a pretty dodgy machine that literally collapsed completely after barely three months. ACtually I have now installed Supernova on her laptop and she's getting on better since she never really got the window eyes commands that well.
I probably ought to try Nvda at some point for interest's sake, though what I've heard of the rather complex commands for basic functions like moving NVda's screen review curser around is a bit of a putoff as is the espeak voice, still I do admire the Nvda project and ought to give it a go just for support reasons.
I did have a look a few years ago at getting a mac with vo and indeed tried one out since I've been quite impressed with voiceover on Ios, though that's probably not going to happen now simply since as I'm now living with someone else my space for extra computers is rather more limited than it might have been. Voiceover looked usable, though a lot of the commands again seemed needlessly complex and the web navigation it had was not exactly streight forward being as tab didn't work in the usually expected way.
Disclaimer! this isn't to say "supernova is the best!" or anything similarly stupid, just that it's what I've found myself able to use most conveniently and do a lot with.
I will say Supernova is far more well known in Europe than America, particularly with it's ability to read in different languages at one keypress (an ability my lady has used on several occasions being as she's by lingual in German).
With our dreaming and singing, Ceaseless and sorrowless we! The glory about us clinging Of the glorious futures we see,
Our souls with high music ringing; O men! It must ever be
That we dwell in our dreaming and singing, A little apart from ye. (Arthur O'Shaughnessy 1873.)