Racing co-axial speedmaster surprise

[hoops10]

Today, I went to the Omega boutique to look at a few speedmasters. The model I wanted to see up close was the Number Edition moonwatch with the manual wind. I have a very small wrist, under 6.5 inches, and thougth that the 39.7mm would be perfect. Tried it on but did not fall in love with the fit. The lugs extended off my wrist ever so slight. The sales clerk recommended the Racing Co-Axial Speedmaster. At first I said it was not necessary thinging it would be much to large. However I did try it on because the sales person said the lugs are slightly different and because I was there might as well try it on. To my surprise it fit much better than the Number Edition. Now I just need to make up my mind on color, but I am leaning toward the black with the black sub-dials. Would apprciate opionions from people that have this watch. Also what is the significance of the co-axial movement. Thank you in advance.