ORIGINAL: sevoblast
The emmitter looks the same but is different internally. Hence the difference in beam dispersion. Changing the installation of the emmitter can affect range, but the emmitter itself also affects range.
As stated, long and involved testing was done, not only lab tests but end user tests for 2 months. Results were excellent.
Difference is manufacturer and price.
Selection is always good. For the DIY guy there is the DBU for $15.00 that can be plugged into any Tamiya system, for even more options.