I didn't post earlier because I don't have any experience with the 2018.
We had a 2004 and I still have the 2012 DL 650. Several trips were made together with both bikes. Both were used for commuting under similar conditions.
Yes, the gen 2 bikes feels MUCH lighter. But it really isn't. All in the bodywork and perception, along with a little less weight up top in the fuel tank
Suspension and brakes for gen 1 vs 2 is a tie. I cannot say the gen 2 suspension was really any better, it was just new and not worn when comparing. Brakes on both are a sore spot for me. Just not good enough on a bike you ride at 75 mph......
Both bikes can be made comfortable for very high mile days. I spent a LOT of time and money getting a windshield to work on the gen 2. The cowling on the gen 2 where the windshield attaches is plastic. Nothing but plastic. So installing large windshields might be an issue over time. Gen 1 and Gen 3 won't have that problem.
Power? The gen 2 was not rated much differently in peak hp. But there is no comparison in real world power! The gen 2 pulls away from the gen 1 in side by side roll ons, agressive take offs, and especially in top gear roll ons.
Fuel mileage. Gen 2 tank is smaller. That still burns my ass. It has at least as good of range as a gen 1 bike. We would fill the bikes up and the gen 1 always took a few tenths of a gallon more and would usually be in the 2-4 mpg less fuel consumption. This is with similar sized riders, both with panniers and other luggage, riding one behind the other.
Now for the non facts....I think the new gen 3 is a really good looking bike. I like how the windshield is mounted. Probably a lot more refined feel to the bike. The fit and finish is improved.
Now to piss off a few readers.....When I bought my 2012 650 I could not say this. I would not buy a 650 today with the 1000 available. There was a time the 1000 was simply not as good a bike and giving up the power by going with the 650 gave you a bike that simply was more reliable, much better on fuel, performed much better all around. That is not true when comparing the bikes now. I would buy a used 1000 over a new 650 if there was a budget limit.
Pretty harsh statement. But the front suspension and good brakes of the DL 1000 make the DL 650 a dinosaur in my book!