Several years ago I decided to replace my 'starter' pawnshop gun (one of the ITW brands: Duo-fast; Paslode is another) as it was pretty worn out and I was tired of un-jamming it.
I bought a Bostitch (N?88; the dual head unit that does the metal hanger nails). I missed one detail that was important (besides round head nails): tool less jam clearing. That's where the head can be popped open.
Anyhow, I used Tyler tools in Texas.
In my research the non-'A' Porter Cable round head nailer (xx350A) had issues, otherwise it was as mentioned: local supply sources (on demand -- most can be ordered). One thing that can be of value is some nailers use a steeper angle on the nail strip. This should mean a shorter overall length.
I talked to my son (framer in Kalifornia) first. He liked the Hitachi for one reason: Home Depot stocked the rebuild parts. He had no other particular reason to like one over another (that he saw on the job site). He did mention that the gas operated (Paslode?) unit was real nice when they had cleaned up for the day but had a couple of nails to put up yet -- the hoses stayed away.
I have the Senco 41XP 15ga finish nailer. Bought it when Home Depot had it marked down. NO oil.
I bought (a couple of years prior) a Bostitch combo brad/stapler (xx100). Some sort of special deal (cordura briefcase style bag and airhose) for the normal price. Works well, but requires oil.
Bought a seized compressor (can't remember the name -- but a brand name for this sort of work) for $5 and a refund if I couldn't get to work (it's former owner forgot to check the oil). A couple of hours with a file, hone (a dowel with wet/dry wrapped around it), and some synthetic oil I had sitting around (the big end of the rod and the crank had seized). It's still running 3 years later. Compressors aren't very complex nor too critical (no combustion going on, and in the few I've been into, no bearings).
On the tool brands, Milwaukee is definitely going the China route since the Japanese company bought them. The new LI-Ion compact drills are made there, and it appears they are making them for Sears as well. Dewalt has mostly continued to be made in Mexico, while the non-professional PC tools are being made overseas (I think the nail guns have been made in Taiwan for some years). Hitachi are almost all made in China now, as I believe about all Makita are too. Dewalt is supposed to be coming out with a new line of Li-Ion tools, and are making backwards compatible batteries to fit the older non-lithium tools (you have to buy the lithium type charger though). So if you bought any in the last couple of years, you ought to be able to keep them for a long time.
Speaking of drills, it is hard to find battery powered drills with the rear handle. I keep limping along with my old PC 12v for that reason (batteries are available, but not replacement chargers). Sorry, of topic.