every motor combination has different timing needs, its not as simple as what year is the best for everyone. Your porting,engine size,pipe and dome all have a factor in what your timing needs are.
The whole reason you have advanced timing and take it away as the rpms increase is because the efficiency of the motor increases with rpms so less ignition advance is needed. Not every motor will need the same amount at a certain RPM it all depends on combustion efficiency.
00-01 are so popular because they are the cleanest setup up the 98-99's and 02-07 have extra wiring with a voltage regulator/capacitor for the power jets and I believe maybe a electric power valve, but 00-01 do not have this.
The 02-07 probably all have slightly different curves like all the other years have shown, but that is not to say they are better or worse it just what works best on your motor setup.
I run a 00 cr125 at +1 degree advance for the best performance (proven on a dyno) out of every CDI that will work for the 00-01 ignition system but that does not mean its the best for you.