Someone can correct me if I'm wrong, I'm not super up to date on cameras in phones. Top android contenders would probably be Samsung, Pixel, and Sony. So I'd probably look at photo comparisons from there.
I like reviews from Mr. Mobile and TheUnlockr when it comes to camera comparison, as they usually put up a two or four way comparison of the top brands.
As far as coming from iOS, photos depends on both the lens and the software, if you like iPhone photos, that's not to say you won't like another, but they're not going to look exactly like that because different companies use different processing in the background.
Thanks for all the work that you do! Voyager is a fantastic app.
Another thought, if it's feasible, maybe also post the apk releases on GitHub? So people have the option to download from there directly or use an app like obtanium to grab it from GitHub.