I've just exported an MPEG-1 file of the same 40 second source material in both RapEdit and Premiere 6.02. In both cases the application accessed the softMPG Ligos encoder I purchased from Canopus. The settings were identical for both exports. RapEdit did it in real time while playing the AVI out to my TV (via firewire/camcorder). Premiere took twice the time and didn't play anything out to TV. The final files are 7011 kb (RapEdit) and 7181 kb (Premiere). Both look identical in Windows Media Player. Does anyone understand why the same codec would perform so much better in one NLE versus another?

It probably has to do with how the encoder has been implemented
in both products. It might even have been that they had access
to the source code and optimized some things themselves.

Who knows!