1, the rules of playing cards are relatively simple and beginners can master them quickly, while the rules of mahjong are more complicated and need more time and energy to understand and learn.

2. In playing cards, players' strategies are usually influenced by the size and distribution of cards, while in mahjong, players' strategies are mainly influenced by the distribution of cards, which may make playing cards relatively easier to master.

To sum up, mahjong is more difficult.