In my opinion neither of those two technologies are effective for white stretch marks. CO2 fractional for off face areas and all over the body has not been substantiated in clinical studies and RF micro needling may improve the elasticity of the skin but the stretch marks will still remain...
You need the right doctor not the right laser. without photos nobody can tell you what is best, but if you want co2 you will want ultrapulse with the right physician. start peels before and after (see link).
at home peels like cosmelan, enlighten and aerify along with dermarolling...