X5000 is the 'better' CPU since Tabor is mid-range and low end is the SAM series (mind you still have to see benchmarks to prove Tabor that much quicker than Sam 460?)
No, Tabor should have an edge in everything except floating point operations.
That's a given.
But at about $450, Tabor is the low end, and the SAM series is irrelevant.
The two core X5000 would be mid-range, while the four core variant would be the high end model.
