The Dittel seems to be a reasonable device at an extremly good price. We have started installing them in our club gliders and are satisfied sofar. Wiring and configuration are error prone, but if you get it right everything works as expected. I have had problems with saving frequencies (it seemd to be buggy sometimes) but this is probably fixed in later firmware versions and I solved the problem for myself by maintaining an excel based frequency list which can be uploaded via a serial interface. Support by Dittel is rumored to be very good, always happy to give advice and short turnaround times on repairs. On the other hand a friend of mine recently complained about sending his radio in the third time in three years. It seems that especially the early models were not yet mature. My experience sofar is limited to the first generation KRT-2.

I don't have as much experience with the Becker, but I am sure it's the better choice if price is not an issue.

You should also think about the Trig. It seems to have the best user interface.

Personally I am also waiting for the air avionics. Unfortunatly the last I heard it most probably won't be ready in time for next season. EASA approval has yet to start and will probably take some time. This information is based on second hand rumors, so I may be mistaken.