I guess I go along with a lot of what's been said about taking some time out before you make a final decision on selling the thou. I know the Fazer can be quite imposing, and, if the suspension is set up badly it can feel quite a handful, but they can be as easy to ride as anything else!
The fact that you seem to feel happier on the Hornet suggests that you've just lost confidence in the Fazer, and, if that's the case, then best to let it go.
Over the years I've gone from 600s to 900/1000s and back again. You don't need a 1000 to have fun, just so long as you have a bike!
In terms of value, a dealer would be putting it up for close to £4k if it's as good as it looks, but privately I'd try for £3500 and be prepared to be beaten down.
Good luck with whatever you decide!