I play both. I have much more money invested in Arena, but on MTGO I play Penny Dreadful which has been amazing fun and the absolute cheapest format I've ever played. There's literally nothing to lose investment wise for PD.
Personally I'm a bigger fan of Arena. It's not super new player friendly, but of the two, it's definitely friendly-er, imo, and you can play completely for free. Also, I'm a big fan of the Best-of-1 format being a thing on Arena. Makes playing much less of a time commitment, which is really nice.
The only thing about Arena that bugs me right now is Alchemy, which isn't something that's necessarily a problem with everybody, but is pretty hard to get away from, unfortunately.
I've played on both at different times. Currently I'm on Arena doing the F2P thing. But the reason I'm not on MTGO is primarily because of tech issues on my end, not any objections to the platform.
I'll agree with everything that's been said so far in this thread. I'd also add that Arena is a more user-friendly experience overall. It has nicer graphics, fewer bugged cards, and it handles a lot of the fiddly decisions for you automatically, like the way it chooses which lands to tap. Veteran or high-level players may chafe at the lack of control or the shallower card pool, but it sounds like that's not where you are in your Magic career right now.
But one of the big drawbacks to Arena is that it doesn't support having more than two players in a game. If Commander is your format of choice then that might be a reason to explore MTGO.
Whichever you choose, having software that enforces the rules automatically is a great way to learn Magic and develop good play habits.
Thanks for the info! I've seen the lack of multiplayer formats as a recurring negative for Arena, but thankfully it's just my wife and I with no real interest (yet) in going beyond that.
I think we'll keep an eye on MTGO, though, because eventually we'll probably want to try something like Commander out. Since we're social distancing enthusiasts it's unlikely we'll look for a local group to play with (nobody in our circle of friends plays MTG) so having a digital option for that will be awesome.
As a fellow social distancing enthusiast, I can certainly appreciate that.
The social angle brings up another important difference: MTGO has chat functionality and Arena doesn't (actually I think Arena does have chat but only with people who are on your friends list, or something). But I'm the kind of person who sees Arena's lack of chat as a positive. I've heard from enough salty opponents to last me a lifetime.
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