Terry, you really don't give enough info to make any recommendations.
If you're using a quality regulated device like a P3 a lower amp cell with higher mah will trip the low battery protections at a much higher voltage than using a high quality 10a CDR cell with 800mah.
If you're using a mech, the higher mah but lower amp rate / CDR cell will cause noticeable voltage drop / sag when the button is pushed.
I wouldn't use any cell with less than an 8ish amp CDR for vaping use, even with the load 13w / 1.5Ω creates.