I just upgraded our old WS to the Horizon EX. The resolution and brightness are definitely an improvement. The Horizon EX has all of the features of the WS plus synthetic vision and built in GPS. I was able to use all of the wiring and AHRS from the WS and it was almost a plug-n-play swap. Another nice feature I gained was the ability to show engine instruments along the bottom of the PFD page.
The only two gotchas we ran into were:
1. GRT's website states that it is a drop in replacement for the WS. That is almost true, but the one catch is that the mounting screws are not in the same place, so we had to move our mounting holes and nut plates. It wasn't that big of a deal, but a little aggravating if you're expecting to go out to the airport and swap them out real quick.
2. The second gotcha doesn't apply to everyone, but it did to us. Because we have an older transponder (GTX320A), we require a grey code adapter to get our EFIS to properly talk to the transponder. As it is right now, we can not squawk mode C. Fortunately, GRT's support guys are AWESOME and are currently in the process of building me one. Hopefully there won't be any issues installing it and getting it to work.
Here are some photos of the old and new.
Caution, the pictures don't do the new system justice. The new resolution and brightness are definitely better, and western Tennessee is pretty flat, so the synthetic vision isn't quite as impressive as what you see on the GRT website.
Overall, I am happy with the upgrade and extremely happy with the service and support I've received from GRT.
Old Horizon WS System:
New Horizon EX System:
New Horizon EX Map Page: