http://www.sapphiretech.com/7000/7000-112.htm
According to this, SDR is indeed slower than the DDR
Let me explain the trick that Nvidia used. They had employed a 128-bit memory bus on the SDR version, and a 64-bit memory bus on the DDR version, so the effective bandwidth was the same.
Now the Radeon VE was available only in with 64-bit DDR memory. However that page states that they use 64-bit bus regardless of SDR or DDR, so the SDR at 64-bit, id imagine, would be a whole lot slower, since the memory bandwidth is halved once more. Most current cards are 128-bit DDR, including the Radeon 7200 DDR and Radeon 7500, and 64-bit SDR memory, at the same clockspeed as 128-bit DDR, would be 1/4th as fast.
As I said before, the graphics processor chip on the VE and the 7000 are identical, except that I dont believe the the 7000 supports dual displays, and also the SDR memory and PCI configurations are new.
Id definitly get the 32MB DDR over the 64MB SDR. Thats just my opinion.