Since the 3DS and Wii U launched I've been exclusively downloading about 95% of those games. Physical media is for suckers. Thing is, you need storage to put all those awesome games on. Nintendo has decided that 32 GB is as high as they can give you to start with, but that's not a lot of space at all considering the new Zelda will take up almost half of that space. The Switch has been confirmed to support up to 2 TB micro SD Cards.
Here's this 512 GB micro SD card for 60 bucks, and it comes with a 64GB MicroSD card that you can use in your 3DS. I haven't seen a better deal anywhere else. IGN currently has a list of micro SD cards from Amazon, and the price for a 256GB is a ridiculous $174.76.
Honestly, this deal seems too good to be true and the website seems a little sketchy to me. But I went ahead and ordered one after I preordered my Switch and it's going to be delivered today or tomorrow. I'll let everyone know if it actually works properly. Right now it's saying limited stock, just 5 left but I don't believe that. We'll see what happens. If it checks out and you plan on doing any downloading at all I'd recommend getting any large SD card.
Here's IGN's list: