i5 by a lot. There are 2 verisions of i5 one is 2 core with hyper threading which gives out another 2threads and of course the i5 quad core with just 4 cores. pentium dual core normally has less cache and is just 2 cores.
He is referring to the desktop version (an actual quad core CPU) and the laptop version (dual core only).
Either way, Intel's current Ivy Bridge Core i3/i5/i7 CPUs are more powerful than the Pentium Dual Core.