Up to you, but the slowfire is a better rifle. It gets through a hell of a lot less ammo than an assault rifle as well.
HEW shops (there's one in MB) and the High Tech Rifle smuggler in TH (I'll let you search for himthough the techhaven website will tell you if you can't) will see to your rifle needs until top level.
And yes, I wouldn't go anywhere near any of the robots until you are much stronger.