I would go with VIAIR also, as like you said, they do have a good reputation. A lot of companies will state their air compressor have a certain CFM, but don't hold up to it. If they do, it may be for only a year, as they use cheaper internals and they wear faster.
All VIAIR specs, will hold true right out of the box and years down the road. Hope that helps, but in my opinion, I would stay with the 300P.
But in no way, am I bad mouthing other compressor brands, just letting you know what I found from my experiences and research.