I have the CED by RSI, bought the chrony, ballistics software, and the optional I/R screens. The IR screens aren't necessary but at least I know that I have them if needed.
The other day I was shooting my .338 on a overcast cloudy day that was drizzling, the chrono was reading all of my bullets without error but it would not read a .223 with the regular sun screens. As for which is moe accurate between the Oehler and the CED, that would be difficult and time consuming to find out...