To elaborate on why I liked it:
The CB650, AFAIK, is an extension of the original 500/550 motor, which is very reliable, as far as I'm concerned. No issues there.
The 650 has CV carbs, which I like better than 'manual' slides like the 550, but it uses the piston-style carbs rather than the diaphragm-style carbs. I like these better, because I never had a piston fail, unlike the diaphragms.
The 82 Nighthawk 650 used the 4-into-4 exhaust, which I think looks great! By those years, all the inline 4's seemed to have gone to 4-into-2 or 4-into-1, but I always liked the 4-into-4.
The 650 had dual disk front brakes, which was nice.
The 82 650 also had a unique set of handlebars - they were two independant bars that fit into the top triple clamp. They were adjustable for height and for angle of pull-back. Very nice. The previous owner from me had them adjusted for a more cruiser-ish pullback style but I was able to adjust them to a more standard feel. Very nice, and much easier than trial and error with a different bar.
Bottom line, it was one of the smoothest, "most refined feeling" bikes I've ridden. Plenty powerful enough for me and still got 55 mpg!
It's almost apples-to-oranges, though. The Yamaha is a twin, with all the advantages and disavantages with that. And, it's a 'special' rather than the more standard style of the earlier models, with all the advantages and disadvantages of that.
You pays your money and you takes your choice...
Good luck with it, whichever way you go.
Kirk