I own a 650 and I'm explore the two lane roads of Nor-Cal, where 60 MPH would probably be speeding. Either bike is great.
I had a 2014 650 and if I rode on roads like yours I would probably still have it. I traded it on the 2010 950 only because I ride a lot of highway miles. In Texas, you can't help it. It's a long way to everywhere and we drive fast.
I was a little concerned the 950 might not be enough since I'm 215 lbs and want to cruise comfortably at 80. It has performed perfectly. I keep up with everybody, the fuel injection has been a joy (starts instantly hot or cold), I get 55 to 60 mpg (more like 50 @ 80mph), and the bike is still relatively light and maneuverable. The 650 carbs and choke worked fine even on cold days, but that only made me appreciate the fuel injection even more. And the 950 actually gets better mileage!
Yamaha did a fantastic job with these two bikes. The 650 was solid. No mechanical or other issues. It felt very well balanced and was a pleasure to ride. The 950 has been solid, too. Zero issues. They are both very good looking bikes. I get lots of compliments. I thought the 650 was a gorgeous bike. See my garage pix. Silver on silver. Dual pipes. The 950 is a really great looking dark red and I think I actually like the 2 into 1 exhaust better.
The drive shaft was my first. It wasn't as quiet as I thought it would be, but it was quiet and beat the hell out of a chain. I was a little surprised the 950 wasn't shaft driven, but the belt has been quiet and worry free.
Floorboards and heel toe shifter on the 950 took a lot of getting used to, but it's second nature now. I like the floorboards.
The 650 has a reserve tank switch which is a pain when you get surprised. The 950 has a low gas warning light that comes on when you have about 30 or 40 miles of gas left and the odometer begins a countdown from 0 to -xx miles to let you know how far you've gone since it came on. I like that much better.
They're both very reasonably priced. I'm happy with the way things worked out. I liked the 650. I like my 950 even more.