Vlad vs. Riven top.

I am deciding between which champion to get for top lane. I know that both are strong and I also know that vlad can play mid better than riven. Which one do you think would be better? I do enjoy champs with higher skill cap because there is more opportunity for outplays. I have played riven when she was on free week and I have to say that I enjoyed her a lot. Thanks in advance.