I highly recommend Makita.
I've got the larger two tank one -
It'll supply air to multiple framing guns at once. It is portable, but it's heavy enough to make it fairly inconvenient going up and down stairs with it.
I end up running longer hoses instead of carting it around in a house for finish nailing.
If I were using it strictly for finish nailing I'd go with the smaller, lighter single tank version.
The Makita's are exceptionally quiet compared to the many of the others, especially the oil-less pancake style. And it'll last a lot longer.
Great quality product, you won't be sorry for spending a few extra bucks for it.