I'm really not sure which would be faster, I'm leaning towards the I3 due to it is Sandy Bridge and gets hyper threading too. Also it's worth noting the mobile Phenom II chips are actually Athlon II processors, they don't have the L3 cache that Phenom II has in desktops.
According to my research very few programs on the market today (aside from huge graphic intense games) are written to take advantage of the L3 cache, so that has never been a concern to me even in a desktop. My understanding of "Sandy Bridge" is that it incorporates a GPU into the CPU. I know this might reduce power consumption, but is it actually any better as far as gpu power then the standard integrated graphics that use to come in laptops?