I'm a bit of a CCG noob so I'm wondering what does MTG offer that Hearthstone doesn't have?
First off, what MTG doesn't offer, but Hearthstone does:
- Grinding games as an avenue to building your collection. Pay cash or go home.
- Game speed. MTG is slower paced, since every action allows for a reaction.
- A 2013-quality UI and animations.
What MTG offers that Hearthstone doesn't:
- Massive card pool. I quickly counted 63 expansions on the Wiki page, each of which is at least as large as the Hearthstone pool. Note that most tournaments use only the 3-7 most recent card sets, but that's still a far larger number of possible permutations compared to HS.
- Non-creature permanents. Think if Hearthstone totems weren't creatures, but another type of card which could only be removed by certain spells/abilities.
- Instant spells and abilities. These can be played during your opponent's turn and/or in response to his spells. Kind of like secrets, except you don't have to play them on the board first, and they activate when you want, rather than on a particular trigger. This means you can never be sure your opponent doesn't have an answer to whatever it is you are planning during your turn, which adds a whole new level of decision making.
- Active creature abilities. Instead of automatically triggering at certain times (end of your turn, etc) and always being random, creatures can have any ability a spell can have and be activated on demand.
- Different combat mechanic. Attacker always attacks hero, defender can choose to block with his creatures. This makes removing creatures with annoying abilities much harder, and along with the point above, allows for significantly more interesting creature design.
- Instead of 1 mana crystal automatically per turn, you can play 1 "land" per turn which creates mana. You also have 5 different "colors" of mana. This has massive impact. You can get unlucky and draw too few or too many lands, or the wrong colors of land (if you have multiple in your deck). You can tailor your deck around having few lands or many lands depending on your mana curve. You can have a deck built around destroying your opponent's mana supply. You can use cards from multiple colors (classes, in HS terms), accessing powerful cards from all those colors, but this increases the risk that you will not get the mana you need.
- Destroyed cards go to a graveyard pile, instead of just disappearing. The cards here can be manipulated or utilized in a number of ways, including be brought back into play, be used to buff up creatures in play, etc.
- Automated tournaments at all hours of the day.
- Sideboards. After the first game in a 3-5 game series, you can exchange cards in your deck with cards from your 15-card sideboard. Sometimes this is used to bring in specific cards to counter your opponent, e.g. board sweepers vs. aggro decks. Sometimes it can even be used to completely change your deck, to outsmart your opponent. You can be a pure spell based combo deck in game 1, and as your opponent sideboards out all his creature removal, you can sideboard in lots of creatures and smash his face in. In general this means fewer matchups are as lopsided as they can be in Hearthstone. You may have a poor matchup against a certain deck in game 1, but by dedicating much of your sideboard to defeating that deck, you can turn the odds around for game 2 and 3.
- Trading.
- Lots of stuff I didn't mention.
Like Ronne said, there are a ton of differences, even if the basic structure is similar. Blizzard should be commended for creating an accessible, fast playing CCG in Hearthstone. As far as strategic and tactical depth goes, MTG is just miles and miles ahead of it. If WOTC would take their heads out of their asses and create an appealing online offering for people who aren't already heavily invested in MTG, they would see a massive boost in popularity and profits.