Never tried swiftkey
but I've got Swipe for my Nokia X6 (best Nokia I've ever had, but that's not saying much) & it's great!
It was a free download from Ovi & I can honestly say that It's the best thing I've ever had on a phone- quicker, easier and more intuitive than either the old school texting, predictive text or qwerty keyboards (both onscreen & fold out as in my N97 mini)