In my humble opinion, like FAA "250 hrs as a PIC or as SIC performing the duties of PIC while under the supervision of a PIC" is more practical and reasonable for ATP.
That standard is only really used in the US, as I said before most places (CAA) abroad won't recognize any time that is not the time where you are in charge and responsible (signing the logbook) as PIC, whether you and I agree with it or think that it makes more sense any other way is irrelevant. Also make sure that the time you spent in line training as a captain for an airline (I.O.E. in the US) is placed as dual received and not as PIC time since the PIC is really your check airman (RTC) he is the one signing the book and even if for all practical purposes you are in the left seat, typed in the A/C and performing the captain's duties, it is still not recognized by most CAA's as PIC time.
Making sure that all your times are accurate and separated into the different classifications that they want is the most laborious part of the application process and there will be no way around it, as I remember I spent a few days of accounting in my logbooks getting all these classifications separated before I could send my application but it was worth it because in all the logbook inspections (they are inspected during your initial application, then inspected again during your training) they never came back to me for some clarification as they do with some guys (is not that there was anything wrong with these folks logbooks, it is just that all the boxes need to be ticked) So use caution!
sorry, just had to throw that in there