the next step up with intel mobile chips would be the i5 chips which are dual core but offer Hyper Threading (four virtual cores). these chips should not be confused with their desktop name sake which offer four real cores but no HT.
the next step up after that are the i7 mobile chips with some being dual core and some quad making the intel naming scheme extremely confusing when jumping from mobile to desktop CPU specs.
Mobile core i3 CPUs also lack Turbo Boost which is only available to mobile Core i5 and i7 CPUs. It is basically an automatic overclock (200MHz - 400MHz depending on the model) and it depends on how many core are being used and the temperature of the CPU.
Generally speaking a 2nd gen Core i3 is 12% more powerful than a 1st gen Core i3. A 3rd gen Core i3 is 6% more powerful than a 2nd gen Core i3. Therefore, a 3rd gen Core i3 is about 19% more powerful than a 1st gen Core i3 CPU. That means an Ivy Bridge Core i3/i5/i7 CPU running at 2.0GHz is basically just as powerful as a 1st gen Core i3/i5/i7 CPU running 2.4GHz.