Wheels have more of an effect over how fast the wheel goes compared to the bearings. If they have a soft PU they are generally going to be slower than harder wheels.
There is really no difference in strength. But I had my mags for a year and they are both finally unusable. (Not good!) They both wore down to the core but never ovalised, chunked or dehubbed in any way. They are also really fast, smooth and grippy. I tried to powerslide and I fell over because they wouldn't slide at all! They were also lighter than my old razor plastic wheel!