Apart from several problems with Traktor over some of the more recent releases (not affecting everyone I think, which makes it even worse), you say your latest Acer easily exceeds the minimum specs, yet Traktor states i5 (which you have) and 4GB (which you have). And you have gone from a 3.1GHz to a 2.2GHz cpu (assuming you are not overclocking, something I don’t suggest doing on a DJ laptop in the first place), losing quite a bit. Also with 4GB being the minimum, I’d always opt for 8GB. Two other things that CAN potentially influence performance are the HD (an SSD is the most surefire way to speed up your current laptop) and the presence/absence of a separate video card. DJ software, among other things, displays stuff like waveforms. While not the most demanding graphical labor, it IS continuously updated screen information. And if your laptop doesn’t have the option of off-loading that graphical chore but has to do it in it’s on-board video, it will take up both CPU power and memory.
Then there are i5 and i5 cpu’s, there are different chipsets handling all the other i/o and memory requirements and such. In short, just comparing two laptops on cpu/memory specs alone is not gonna tell you much about (expected) performance.