What is better? Fractional Co2 or Sessions of Microneedling?

I often combine Co2 and microneedling with prp to get the best results and often do these treatments on the same day. I recommend getting a formal evaluation with an expert. Best, Dr. Emer 

Fraxel Re:Pair is a CO2 ablative laser that not only creates microwounds in the skin (as does microneedling) but also heats the collagen to contract it and tighten the skin. It is a much more effective procedure than microneedling alone. Although there is never a guarantee, combining the two therapies could make a really dramatic difference in your skin. If your budget won't allow that, then I'd suggest going for the Fraxel and arrange for a payment plan, if necessary. Please see a board-certified dermatologist for your Fraxel to get the best results.

While microneedling can stimulate collagen, the amount of collagen is not equivalent to a fractional CO2 laser.  Partly because the CO2 laser not only ablates the skin (vaporizes the multiple microspots) but also delivers thermal energy which is equally needed to stimulate collagen.  The depth of penetration is precise.
There is a different in cost and downtime however.  Fractional CO2 will carry a higher cost and also have a longer downtime (typically 3-5 days of social downtime, depending on energies utilized), where as microneedling has a lesser downtime, but also a less of a result.
Hope that helps!