Ok, I guess you can say that Steel Force and Magnum are similar in the respect that both were built by Cedarfair and severed similar purposes. Because of this, many of the elements in the two are similar.
At the same time, the coasters are no where near alike. Where on Magnum are those underground tunnels? Their helixes are completely different, as well as the design of the return hills. I would have to say that Magnums are more of a bunny hop, while Steel Force makes use of camelbacks. In my opinion, Steel Forces back side is far superior to Magnums, and the overall ride is more enjoyable due to the couch-like Morgan trains, and smooth ride. The ups Magnum has, is the scenary, which one cannot beat, and the fact that you realize you are about to embark on a bit of history as you crest the hill.
In conclusion, both rides are great, but Steel Force is just a better, faster, smoother, and more enjoyable ride.