I Think they are almost as same as CoC but quite easy to earn and also builders are not attached with crowns so you can buy the builders with gold. Like in CoC crowns can be used to finish the task instantly. Diamonds are difficult to get for trading.
Gems from clash of clans are more useful because they can be used in many different ways (boosting your collectors, the training speed of your army ...)
It's different for crowns, because you can use them to make your construction instantly and getting ressources, but that's all. You can buy the rest with gold, so they are less important and easier to earn ^^