<< Nope. Less bandwidth than sdr mx. The ddr mx is only 64bit >>
Yes, bus is only 64-bit, but since DDR is twice as fast, it makes up for it. (so they do have the same bandwidth)
As for performance, it's true SDR should be a little faster because of latency issues and other things with DDR, but it's probably unnoticeable in real world.
Bottom line= get the cheapest MX you can find (with good overclockable ram)