I hope I can clear this up for you. Brads are small (half-inch to two-inch long), thin finishing nails, usually with only half-heads that embed into the material; some brads are even headless, working more like tiny, straight staples.
Most nail guns can be loaded up with brads, and it sounds like your air compressor's nail gun is capable of accommodating various sizes of nails, including brads.
If, however, you require a nailer than can house larger nails (assuming your model only holds brad-sized nails) and you decide to buy a new nailer, and you're only using it for around-the-house fix-ups, you don't need to spend more than, say, $150.
When air nail guns first came on the market, the price and variance in quality was great; nowadays, most brand-name models are basically equal in quality and price when it comes to basic usage, the type you're talking about.
I hope this answers your question.
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