The real distinction for the Switch's "cards" is that they are a physical medium with no moving parts. This makes them far better suited to a portable device. It is why Nintendo has always stuck to cartridges or cards for its portable devices. Sony's experiment with UMDs on the PSP was a mistake, and they adjusted hard with the Vita. Granted, this didn't particularly improve the Vita's chances, but I don't think the Vitas physical media format was to blame for its failings.
Physical cards have faster data transfer compared to optical media, they require less power, and they have no moving parts. (less likely to fail, more stable hardware) All of these advantages make them well suited for portable systems. The disadvantage is that you usually get less memory for your money, and the format is generally more expensive per title. Optical discs can be printed in factories to the tune of pennies on the dollar. They lend themselves very well to rapid mass-production. Cards and cartridges are more physically sophisticated, and require more complicated production. Their per-unit cost is always going to be higher than optical media. Also, modern optical discs (usually based on blu-ray) can contain an obscene amount of data. A dual-layer blu-ray can store around 50 gigabytes of data, and the blu-ray format can go higher than 2 layers. Even some of the largest games today usually don't break those numbers, making optical media an affordable standard for stationary systems.
The one worry from the Switch's media choice is that it will be less likely for there to be games that launch at lower prices. ($20 or so) The per-unit cost of cards means a lower mark-up for each physical copy of a game. Publishers are motivated to sell their games for more on the Switch, and to not be in a hurry to lower the prices on those games too quickly. I do worry that we won't see nearly as many sweet deals on Switch games, especially given the tendency for Nintendo's first-party games to hold their value over time.