I'm just gonna put this out, please don't super bash on either one, everyone has their own opinion but please don't be unnecessarily rude. I know Log Horizon is still airing so it might be a little hard to say just yet, but I feel enough episodes are out that a person could cast a vote, and hey feel free to change your answer then if Log Horizon has a terrible ending or something idk.

I would say sao since it first came out and also since horizon has somewhat similarities as sao as well as story plotting , but both are great animes in my opinion

I like them both but I like SAO a little more because Log Horizon kind gets boring with everyone is pretty much a 91 or 90 in it and you can die and not actually die