I know you're familiar with the 650s little brother, the DR-Z400S bug out bike. Used in military service in several countries. Almost 60 mile per gallon, huge engine/ground clearance, go nearly anywhere, light weight, tiny carbon footprint, 1 minute to refuel, can install racks, and if necessary carry a passenger. Same engine/model made for past 20 years. Total proven product/reliability.
In real tough times, these are a great asset and a blast just to cruise around on.

Btw, I came very close to getting the 650...Super bike. I opted for something and bit smaller/lighter and the 400 fit the bill.
I have a Yamaha SR400. It's a fuel injected thumper oriented to riding on the street. 66 MPG with regular gas. Kick-start only with a decompression lever. Not quite as finicky to start as my old BSA 500. Lower compression and less horsepower than the BSA. The DR400 package that I admire most is the super-moto. I might have gone that way, but my Versys with 17 inch wheels front/rear fits that niche just fine. I went with the bush pig to have a dual sport that can work competently on the street or dirt. The other bikes in the garage are really street bikes.
I really admire the hot 450 singles, but the seat height is out of range for a 30" inseam. Besides, I might forget I'm 65 and do some things on a motocross track that aren't age appropriate :-). The DRZ400 is a sweet bike. It will treat you well.