3.5 bar or 10 bar

[gazwhittle]

Hi guys making the upgrade from flux core to a gas setup.

I'm buying argon+5 from my local gas guy along with an argon regulator.

Only problem they are asking do I want a 3.5 bar or 10 bar output ?

I have no idea what this means so which should I get. It's for mig welding mild steel indoors.