Omega co-axial is a good movement. Long term accuracy is very good. It's very stable. I didn't rate it as great becoz my personal experience has been rather disappointing. My Bond SMP has a co-axial 2500C which is great in term of accuracy stability but reliability was a bit of an issue. Mine has intermittent issue during warranty period and finally stop running just after 3 yrs. Send it back to Swatch for repair and cost me almost 1k. But then again 2500 is first generation co-axial unlike the current 8500. They could hv improved and fine tuned it a lot by now.
For the Speedy, personally, I would love to get the original with the hesalite front and cal 1861. Staying true to the moonwatch DNA.