[cairo] Non-antialiased rendering in image surface

[cu]

After the previous set of issues with non-antialiased rendering, there
is a question that I think went unanswered.
Someone mentioned "non-optimized code path" "with a1" - I didn't quite
get a reference, so I'll ask directly:

Is there something about non-antialiased rendering that makes it less
preferred or slower than antialiased rendering wrt image surface?