Both are good. I prefer the Clear Nav. The CN controls on the stick are easy to use and soon become second nature. No reaching for a touch screen. Tunnel mount is a nice installation if your panel has the room. Once you get the performance dialed in, the ameba pattern is an easy, quick glance and accurate decision aid. I've never flown with the Oudie but have with an IPAQ. I now have two gliders and both have clear nav installed.
If you do install a CN, dont let direct sunlight hit on the screen for long it will burn the screen. One reason the tunnel mount is my preference. I've seen two gliders with tilt up canopies that had burned screens after the the canopies were open for a spell with the sun shine directly on the screen. I cover mine with a towel on the ground.
Oudie screen may do the same, I dont know.