the galaxy 919, 929, 939, 949, and 959 are all the same radio on the inside, some have options the others dont, like SSB, the starlight faceplate, freq counter, etc...
as for the differences between them and the cobra 29LTD, i have run both types and both will work just fine. both seem to stand up to heat and vibration ok.
both can be made to sound great on TX.
i think the galaxy radios have a noisier receiver, but they do have the big meter, so...
LC