If I were prone to flats I would use a pump too.

Used a Zefal frame pump for years and still use it with my single speed road bike. I could never seem to get enough pressure with it and find I would abort the ride and return home after using it.

Only had to use the CO2 once and it worked, pressure was really good so I continued with my ride.

I think local road conditions should be a guide. But for me, so far, CO2 seems to be advantageous.