Doesn't matter in a quality gun. Just personal preference. Do you like where the safety is on the gun? Do you like a flat or stepped rib? Do you want a gun that shoots to bead or do you like to float the target? These are more important than inertia vs gas.
Inertia guns have a problem with the bolt coming out of battery, but you fix that with a spring upgrade. The point above about staying with a gun that will be similar to what you already know how to shoot is a good one.
