I think I would go with Selenium. I don't know Telerik but I do know that:
As of early 2012, Simon Stewart of Google (inventor of WebDriver) and
David Burns of Mozilla are negotiating with the W3C to make WebDriver
an internet standard. As such, Selenium-Webdriver (Selenium 2.0) aims
to be the reference implementation of the WebDriver standard in
various programming languages. Currently Selenium-WebDriver is fully
implemented and supported in Python, Ruby, Java, and C#.
Of course nobody knows if it will become a standard but the fact that is under consideration gives me hope that what I learn using it will be useful in the future. Anyway, it's an aspect worth keeping an eye on.
Also, I could do what I needed by reading their documentation.