As you could expect the memory performance is much the same on both the Gigabyte M59SLI-S5 and ASUS M2N32-SLI Deluxe. While SiSoft2007 did give the M59SLI-S5 a slight edge over the M2N32-SLI Deluxe, there was really nothing in it.
The nForce 590 SLI boards appear to be roughly 300MB/s faster than the older nForce 4 SLI board. The PCmark2005 results show huge memory bandwidth gains when moving from the older K8NXP-SLI motherboard to the new M59SLI-S5. In fact, the M59SLI-S5 delivered roughly 23% more bandwidth than the K8NXP-SLI according to PCmark2005. MemTach on the other hand showed almost no performance margins between all three motherboards.