A very happy LX9000 user here (with Flarm/AHRS/2nd seat display), with limited experience only in other people's 2 seaters of Clearnav and LX8000. As a previous LX7000 and Oudie user I found it easy to use, but starting from scratch the Clearnav is definitely easier. I much prefer the control system of the LX9000 using knobs and soft buttons to the Clearnav remote control (I know that not everyone agrees) Most things I do in flight such as zooming in and out, or changing between continuing on my task or going to somewhere else, perhaps my home airport, require many more steps in Clearnav. I like being able to choose my own setup, so for me the philosophy of greater flexibility works better than the Clearnav philosophy of simplicity. I like having my IGC files automatically on a full size SD card. I like the very tidy screen layouts available. I consider that the screen size is optimal - for me the LX8000 is too small for the amount of info it tries to display, let alone an LX8080, I would rather use an Oudie. While I would be happy to have the 7 inch and 8 inch displays now being offered I cannot imagine fitting them on a glider panel with all the other stuff I would still want, and 5.6 inches is big enough for my eyes. I find that the LX9000 is an integrated device which does everything well, and with no disadvantages if you are prepared to do a bit of work on the setup.
The LXNavigation Zeus seems to do all the same things as the LX9000 but is a much less well proven product.
In an expensive new glider it may be worth investing in these high end systems, and I expect you would be happy with either Clearnav or LX9000. However, I find it difficult to justify the price difference from eg a v7/Oudie combination (or for even less money XC Soar running on a cheap device) with the logger choice depending how you want to get your Flarm data.
Good luck choosing, and do report back.
Mark Burton, London Gliding Club, UK