I've played Darius a couple of times when free to play but I've seen Cassiopeia a lot in the LCS lately and considering her. I have enough IP for either but I wanna know your opinion and why you think that and maybe leave a couple tips please :)
Darius is fun but is kited into oblivion and struggles to carry. But, dunking is so fun.
Cass is crazy strong if you are really good with her but her passive is boring and her entire play style is land poison and then spam the hell out of twin fang.
So... do you want fun or a strong champion?
They are completely different champs, so without knowing your preferred playstyle it's hard to give that sort of advice. Cass, while she has fabulous sustained damage and an ult that can really set up a teamfight, she'll take a lot of practice before you really get good at her. You have to get used to watching your target to make sure they're poisoned for your e reset, the q has a delay that takes a decent degree of predicting, and she doesn't really have a reliable escape. She is not a burst mage, and trying to play her as such will result in your death.
Darius is a ad slaughterfest, able to do damage while still being a bit innately tanky. He is the cleanup crew, but like Cass has low mobility and a bit of a learning curve. He has few difficult matchups, and can deal out the damage, but also be prepared to deal with people who will bitch you out for ulting someone as a "kill stealing jerk"
I say Darius, A) Because i main the hell out of him and you can get double kills SOSOO easily with him if you get first blood, and B) Because Darius has good engages, is fun to play, and can be one of the most op champions if played right.
Dunkmaster
Is so sexy as well, you might as well get it ;)
I tried Cass because he is a strong midlaner and a hard carry, and I am still practicing with her. It sounds so easy, poison enemy then spam E on them, but it really isn't. Her difficulty rating is quite accurate.
