I'm going to get both of them as I do that with every pair. I will get one of them before the other though, but I have not yet decided which I will start with. In the past, I have started with one over the other based on several different factors. Those were: the color I liked better (Blue, Silver), letting a friend choose and starting with the other myself (Ruby, as my friend picked Sapphire), based my choice on which version exclusives I like better (Pearl, Black) or which cover legend I like better (X). But this time, I'm not sure how I'll do. I don't think I will get to know the version exclusives before the release (and I don't want to spoil myself for them to be honest). Then I don't really prefer either legend over the other when it comes to design. So I'm not sure which game I will start with. I'm a little more biased towards Moon at this point due to influences from other media, but still... haven't fully decided yet. I have more than half a year left to make my decision though, so it isn't that bad. I'll know sooner or later.
I'm definitely getting both games as physical copies because I prefer having a physical copy of all my games. Never tried a digital copy and I fear the time it takes for them to download might be too long for my tastes.