GRX Di2 vs Ultegra 12speed Di2

[PaMtbRider]

Has anybody ridden both and have a strong preference one way or another? This will be going on a 650B gravel bike.

This will be a double chainring setup with an aftermarket crank so gearing options don't come into play.

I prefer the looks of the Ultegra and the semi wireless aspect, plus it's 12 speed so it has to be better

GRX has the benefit of a clutch rear derailleur. This is the one big plus so far since this will occasionally see some chunky gravel.

I think they both have servo wave braking. Are there any other differences I should know about?