The art is just as good, it's just a completely different style. I've seen brilliant pieces and stinkers in both WoW TCG and M:tG. Magic's art style would look out of place in a WoW game and people upon seeing the cards would basically just say "it's exactly like Magic but not as good" or whatever (though people do that now I guess).

As for gameplay, I haven't actually played M:tG since the Mirage block fifteen years ago so I couldn't say but I do know that for somebody attempting to get into a TCG, M:tG has a leg up with popularity, but WoW has the advantage with affordable competitive decks and is far more newbie friendly. I personally love the fact that the game and its characters are actually recognizable and mean something to me without having to read shitty books that are only interesting to total fanboys (though I still have the option too :P).

Also, from where I stand, playing the hero on a card is more interesting than playing as the wizard casting the spells but that's purely preference I think.