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The 9700 non-pro is quite a hell of a lot better if they're the same price. Even if the 9700 was a bit more expensive it woul dbe the better deal.
Clock speeds as raw numbers mean nothing.
Look at processors, an XP1700+ runs at 1.43GHz and outperforms a 1.8GHz P4 (IIRC), the same is similar for graphics cards.
The FX5600 is the mid range part, the 9700 is the lower clocked high end part.
The 9700's memory is 540MHz (270x2 to reflect the fast it's DDR) which is only 10MHz lower than the 5600U, I believe it also has double the memory bus width anyway, 256bit compared to 128-bit, so it has about twice the memory bandwidth.
That 5600FX is also the slower version, there is a new one clocked at 400/400 which still is worse than the 9700 non-pro.
Get the non-pro. In fact, get loads, you could sell them for $180 at least.