The best choice mostly depends on personal taste. Typically, physical copies of games are cheaper as you can find many older games on sale at various stores. However, sometimes Nintendo has sales on its digital eStore, so you can buy such titles for less. Ultimately, it depends on your personal preference. Digital copies mean you don't have to worry about carrying a game cartridge with you, but they also mean you can't swap games with friends or choose to resell them once you've finished playing them. You can resell physical copies if you wish, but they don't have the convenience of always being available on your console without needing to remember to take the cartridge with you.