Never tried Cockatrice, to be honest. I use xmage at home, when i'm looking over my cards, mainly to see what I can or cannot do, because some friends of mine also use it for playtesting (and not burn money on really useless cards at our LGS). Sadly can't get it to run here at work (actually using my phone to go to deckstats lol).
As for Xmage. It's a substitute for MTGO, I guess. It has the same lag and bugs, if not worse. But it's free. And you can set up your own server if you want to.
Tell you what, as soon as I'm able to connect to xmage i'll pm you so we can playtest these versions. See which one runs better