Good question. Tough question. I'm going to have to go with the Babolat SFX. Mainly on the fact that I haven't worn the GR5 shoes that much. However, I've always been a huge fan of the Gel Resolution line.
I choose the SFX for the following reasons: they fit my feet better (wider, lower arch), the cushioning is plush but responsive, supportive and stable.
Now, I might have to change my answer once I hit in the GR5s more, but for now, I'll stick with the SFX.