We'd give the edge to NVIDIA because of their strong NCQ performance and support for SLI, but those two items aren't necessarily on everyone's shopping list. For a lot of people, SLI is too big of an investment and a lower priced motherboard is far more desirable, not to mention support for TM2 on dual core CPUs for a cooler, quieter system.
The fact that this decision is so very hard is a testament to NVIDIA's strength as a chipset manufacturer. In fact, we've never seen anyone threaten Intel with nearly identical specifications, nearly as much as NVIDIA has with their nForce4 SLI Intel Edition.