As mentioned over in the MtG thread, Magic Arena aims to be a proper MtG experience on PC and mobile devices, rather than the cut-down experience of Magic Duels or the ancient and PC-locked experience of Magic Online. To that end:
-Full deckbuilding options within the sets available in the game, rather than a limited selection of cards and limitations within decks based on rarity.
-Unity-based, so they should have no problems with getting it to other platforms.
-Booster Draft and Sealed play options, a huge boon for the game. Getting a group together for Limited formats in paper Magic can often be an ordeal, due to the initial cost associated with buying boosters for a tournament, as well as the different skillsets tested (on-the-fly card analysis and speed deckbuilding) compared to Constructed formats.
-Developed by a new internal dev studio, with talent from studios like Dire Wolf Digital (Eternal and the Elder Scrolls digital CCG); this should, if nothing else, avoid some of the issues the Magic Duels games had over the years under an external studio’s care.
-No specifics yet, but WotC is looking at ways to tie the paper Magic experience with Magic Arena, such as giving in-game rewards for attending prerelease events at your local shop. The ultimate win here would be if they take a cue from the Pokémon TCG and include codes in physical boosters for a digital booster from the same set, but this seems unlikely.