I had been a Hearthstone player for nearly two years and because of recent events decided to move on and try out MTGA with no prior Magic experience. Wow, I am glad I did! In terms of variety, technicalities, interplay, and strategy MTGA has Hearthstone beat. A few things that Hearthstone has over MTGA is lore, the mana or land system, and the platform isn't nearly as buggy - disconnects occur more than they should.
The best thing in MTGA favour is the game's economy system. Don't get me wrong, the grind is very real for the pure F2P player. However, your daily and weekly rewards are more substantial, you get to accrue packs a whole lot faster, and overall the value per pack is better. The cherry on the top is the wild card system which replaces and eliminates the need for dusting which is not even an option so your collection can only grow. But I'll be honest, I have spent about $200 on the game which amounts to about 180 packs. I knew by week 2 that I'd be playing MTGA indefinitely and wanted to grow my collection substantially which it now is.
MTGA is great fun and value for the time and / or money you put into it. Try it and you see what I mean!