Hearthstone

Easier to learn. There's still depth, not the level of M:tG, of course.
As said earlier, watch trump play, he's streaming now: http://www.twitch.tv/trumpsc
There's a 'low' amount of cards at the moment, obviously. So relatively the amount of different strategies and decks isn't as varied as M:tG yet.

In Magic, I really like decks that keep my opponent's board state under control via burn spells and countermagic while rapidly blasting away their health with more burns and creatures that synergize with spell play like Guttersnipe. I usually play RU or RW.

Which classes best match this strategy in Hearthstone?