Glad you are having fun with your bike. I haven't heard of any difference in power generation between the SON & Shimano dynohubs from the randonneur crowd and they usually uber picky about such things.
I've had both and still own a Shimano - works fine. I'd buy another without hesitation.
This is my fourth Shimano dynohub, but the first time I've tried running twin headlamps. I'm going to swap out one of the lamps and see if I can get better preformance. I've been more than happy with all my other Shimano hubs.
One side of the panniers is in a St. Simons landfill (the bike has been on in the ocean now--had to replace all the rack bolts, they rusted by the end of the day). I'm going to put a stiffening board inside the surviving one and put some Ortlieb attachment hardware on it. After that it will be much more functional.
And I'm going to have to get off my but and build some fenders for this thing. Good lord, it leaves the most impressive of skunk stripes down my back.