I've always felt that the spelling 'magick' was a pointless gimmick.
While this spelling might have some historical precedence, its modern usage, to the best of my knowledge, was instigated by Aleister Crowley. His reasoning was simply to distinguish 'proper' magic from stage variety. Not something I feel is particularly necessary today.
But somehow, when I started writing this blog, I ended up using the spelling. I won't lie to you. I think it's probably just as much mock pomposity than anything else. And partly it is probably influence from texts I have been reading recently.
Anyway, both forms are actively used by occult writers, and there really is no particular difference in their meaning, at least for most people. So use whichever form you wish, or both alternately, or whatever tickles your fancy. Nuff said.