Hands down HPA is better in every way than CO2 but it all depends on whether you can have access to it or not or even maybe purchasing a tanks since they are all very expensive compared to CO2 tanks.

I use both at the moment just because i have 2 20oz CO2 tanks and 1 114/3000 HPA tank. As soon as i get the other HPA tanks plus a fill station. Bye bye CO2, HPA in my local shops is 6 bucks, i rather use that money onto something better than just air lol, plus for 5 bucks i get a 80cf tank filled.