Its quite common for there to be slight timing differences between different brands of converters(I found similar when combining the 003 with a lightpipe preamp). The only time that tiny offset is really going to matter is if you are running the same signal thru both converters
I work with a pair of HD IO boxes and a 192 here and have yet to hear anything(certainly the HD IO would be the same as the OMNI). I measured 8 samples of offset between the HD IO and the 192 here.(snare mic thru 2 preamps, 1 thru 192 and other thru HD IO). The preamps are different brands but all analog so I don't know if there is any difference in either preamp's throughput