It's just a better all around CPU. The 699 model has 1GB less RAM so for Vista to be happy you want that extra ram.
I can get a Dell 1520 (Intel Duo Core 2 1.6, 2GB, webcam, DVD writer, everything else standard) for $809 OR Best Buy has the Toshiba A215-S4747 (AMD Turion X2 64, 1GB, DVD writer, etc) for $699. I have had a Toshiba Satellite 2455-S305 for four years and it's been great.
So on the surface it looks like the Dell is the better performer and it would cost another $50 to upgrade the Toshiba memory reducing the price advantage on the Toshiba. Is the Dell a good buy? Is the Toshiba better quality and likely to cause me less problems?