@alexo - per the other thread you opened..
Note2/3/Air comparison video.
However, the OP wants to know how much better are Note2/Note Air/Note3 than the original Note, and having a Note Plus (same hardware pretty much) , I can tell you that the PCMark on that device comes in at 2781 on the Work 2.0 benchmark, versus 6295 (or thereabouts according to my deep guide) on the Note2/3/Air trio.
So roughly speaking the newer models should be twice as fast. That's the theory anyway, but I can tell you that as I happen to have a Note2 at the moment as well (because I'm upgrading, and not because I'm a marketing person in disguise on Youtube), the actual reading and notetaking and browsing performance is pretty much the same between the original device and the newer ones.
It also helps that you can run the latest 3.0 software now on all the Note platforms, so unless you want certain hardware/OS dependent features (e.g. fingerprint reader, backlight, gestures, split screen etc) then it is probably not worth upgrading. I wanted the newer features but didn't want to pay for the latest latest models, I'll take the 100 bucks I saved and spend it on eBooks and beer!