I'm a bit partial to the 345 myself. As Alan mentioned, a search for the checklist will help you know what to look out for when inspecting a unit. The good news is that the P30 chassis have a god reputation and highly available and inexpensive parts supply in the automotive aftermarket. For more information about the models, years, layouts, and some history check out another member's website: www.airstreammotorhomes.com
Airstream motorhomes definately do not have a lot of storage. They are narrow, low in height and you are correct in that the rounded curves mean no large overhead lockers and no "baggage" door lockers on the outside. Despite this, they can carry quite a bit of gear (we typically travel on short trips as a family of five) but you'll learn to pack well and come up with tricks to maximize storage ideas (a closet rod in the shower for example doubles as a closet most of the day).
As far as the handling goes, I've driven other SOB motorhomes, same year on the P30 and absolutely believe the Airstream behave better and are less stressful to drive. They aren't a diesel pusher, but there are much better than most other brands on the same chassis built during those years. I would say however that a modern gas motorhome on a W22/W24 would out perform the classic, but who has $150K for a gas motorhome?
I think it's the combination of air bag assist along with the tag axles and the lower profile, lighter weight of the Airstreams. After driving one particularly "boxy" SOB across Mo, I can also say there is a lot to be said for curved sidewalls allowing ar to "flow" around the body.
Keep us posted on your search. We've all spent a lot of time driving, camping, sleeping, eating and working on in around and sometimes under our Classics. You'll get a lot of good advice around here.