All I know is the 617 is available as is pump rebuild kits. If you get one, you won't have to worry for a looooong time as they are serious long life tools. By the time it becomes obsolete, maybe the china bunch will evolve into a quality product.
I have a t-635 and it is a very good unit. It is quite a bit louder (3450 rpm) than the 617 but still a lot quieter than the run of the mill china junk. The reason I got the 617 is because the 635 does not like to start on my honda eu2000i generator. The 617 starts easily with my eu1000i genny so it goes with me in the van.
As far as easy to move around, the only thing I know of lighter is the senco 1010, of which I own two. Problem with senco is I need to run a senco SKS staple gun which leave it out of air and you out of luck.