First off, the Nikon's feel like about half the weight of the Canon's in hand. The Nikon's feel delicate, the Canon's bulky. Neither unpleasant, just hugely different when switching back and forth between the two.
The Nikon's are sharper. Period. The Canon's I had to struggle for best focus, the Nikon's just popped into the sharpest pinpoint stars you can imagine. Now it's not that the Canon's were that BAD, it's just that the Nikon SE's were that much better (even with the IS off).
The Canon's had a slightly narrower FOV than the Nikons, expected with the higher magnification. The Nikon's also had better contrast. The sky through them was simply blacker, that kind of velvety black you associate with the very best optics. In comparison, the Canon's appeared to have some skyglow present. HOWEVER... which do I prefer the view through?? The Canon's, because once you hit that magic "IS" button, the view just freezes, any shuddering/ jittering goes away- and the view just floats there. Float is, in my opinion, the best word to describe the view the IS gives. There is no way short of mounting the Nikon's (or perhaps in a lounger) that I could get anywhere near as stable of view, and to me, the jitter that you're going to get handholding 12x optics is unpleasant. Even leaning my head back against my van in the driveway and bracing my arms couldn't provide adequate support to provide the stability the optics cried out for.
Now on the moon, the results were different, surprisingly. Both bino's focused well on the larger target; While the Nikons still seemed to focus easier, the Canon's still came to an equally sharp-appearing view. The Nikon's exhibited slightly more green CA on the edge of the moon, while not objectionable, it was still there- and more prevalent than in the Canon's, which showed almost no CA. The Canon's handled the brightness of the moon better as well, giving an equally pleasing presentation- only larger. I was unable to notice the difference in the black sky background I noted on the starfields. Overall, the lunar view was quite a bit/definitely more enjoyable through the Canon's, not only because of the increased magnification, but more importantly, to see the moon just floating there- as opposed to the little jitters that the unstabilized view through the Nikons give at best handheld.
My overall favorite? The Canon's. It's just so much easier to get an enjoyable view through than the Nikons. The Nikons, while exhibiting better optical quality, need to be mounted to fully benefit from the improved optical quality in comparison to the Canon's.
Oh... one last comment: I've always been quick to point out lousy objective covers- that don't fit/won't stay on... well, these eyecaps on the Nikon SE's are at the other extreme- Lordy, I had the hardest time getting them off. They simply aren't ever going to fall off accidently or in the case! WAAY too snug. Why is it so difficult to make objective caps that fit properly???
Next in line is a comparison of the Nikon 12x50SE's to the Canon 10x42L IS bino's, hopefully tonight.
Hopes this answers some questions that were finally asked yesterday.