[cabmandone]

For what you're doing, Harbor Freight will be just fine. If you're worried about it, buy the cheap extra replacement insurance. The notched vs full is a minimal consideration for me. I have a Bostitch that uses the notched nails and have framed several garages with it. I guess it boils down to which nail type is more accessible. The Bostitch nails are more expensive and I've found that the nailer doesn't like many of the no name nails out there.
The way it sounds, you're framing interior walls in an already built pole barn? If so, don't spend the money on 2x6. You can get a decent R value out of an interior 2x4 wall. I have my heated and unheated space separated by a 2x4 wall lined with 7/16 OSB on both sides and the heated side stays above freezing here all winter except on the very coldest days with no heat turned on.