Two things about fonts.
1.) People who grew up in the 50's and 60's, like me, find serif fonts
easier to read, since the books we learned to read in were written in
them (Yes, good ole Dick and Jane!). My kids generation learned to read
in sans-serif fonts, so they find those easier to read. So to some
degree, it depends on who your audience is and if they're of a specific
demographic. If not, who knows?
2.) Monospaced fonts are harder to read, though give consistent widths,
because most readers don't read each letter, they read the overall
shape of the word. Since most of the world uses kerned fonts, part of
the shape of the word is determined by the width of the letters in that
word.
I pondered this question years ago when I was working on some printing
projects, and came to the conslusion, after some research, that's it's
very difficult to make hard and fast statements about which fonts are
more readable. There are so many factors that it's really a crap shoot.
Now, I pick one I like and go with it, and hope others can manage. YMMV.