When it was designed it was intended to be faster, but actually, the differences are not relevant for real-time applications with standard cameras. By the way, FAST detector is faster and quite robust.
I am programming for real-time augmented reality on phones, and we use a combination of SIFT (initialization) and FAST (pyramidal FAST for real-time feature detection) during the application execution. FAST is faster, and it is implemented in OpenCV, so if you don’t want to stick to SURF give it a try. I haven’t seen recent papers that use SURF for real-time but I have seen modified versions of SIFT, with fewer pixels for descriptors and other kinds of modifications, so it seems like SURF was kind of a great idea that didn’t get as far as it was thought to. That is just my opinion, anyway.