I try to alternate. I rode the 390 last weekend and planning to ride it next weekend, so figured it was a good day for the GW.
Felt kinda weird rolling up to the "fast" bike group on a GW though. Was happy to see another one there. The GW has no problem keeping up with the fast bikes though, but to be fair no one is going that fast. Unlike North Texas where we ran pretty fast on group rides.
(Side note, I didn't realize that when I started riding in North Texas that I had jumped into a group of such really good, fast riders. Just happened to fall in with a bunch of old racers that can really ride. So, I got used to a really high group ride pace. Down here, I haven't ridden with a group yet that all goes the type of pace we used to do regularly in North Texas. Sander can definitely ride that way, but by and large, the vast majority of groups I've ridden with down here are considerably slower by comparison. So I don't feel the need for super fast bikes here.)
Back to your question, if I know there is dirt or lots of dead ends on the ride, I'll take the 390.
Otherwise, the GW is pretty nice for a long paved ride. I just have to remember it has its limitations in corners at speed. I've started scraping the pegs on it pretty regularly lately, when I ride solo.