Well i'm going to have to debate that point.
DualDDR Memory Architecture
DualDDR is able to deliver the highest overall system performance for both integrated graphics systems and systems with graphics add-in cards. The NVIDIA(R) nForce(TM)2 DualDDR memory architecture optimizes system performance by increasing bandwidth and reducing memory latency.
Features of DualDDR memory architecture include:
Highest memory bandwidth: DualDDR combines the power of DDR400 with two independent memory controllers, which yields a staggering 6.4GB per second of memory bandwidth—twice the memory bandwidth of other DDR400 chipsets. Increased memory bandwidth delivers better system and graphics performance, resulting in more overall productivity.
Lowest latency: Both memory controllers operate concurrently with each other to hide latencies associated with typical chipsets. For example, controller "A" reads or writes to main memory while controller "B" prepares for the next access, and vice versa. As important is the second-generation DASP (dynamic adaptive speculative preprocessor), which has been re-architected for improved performance.
Most stable and flexible memory system: End-users can now populate higher density DIMMs, up to 1GB each, to utilize the entire 3GB memory address map. This large memory map allows more applications, audio and video streams to coexist without conflict.
So Contrary to what you've been told DualDDR is the way to go to improve overall preformance for your system.