not sure why people are still getting Spektrum nowadays, they are famous for having quality issues and glitches, get yourself a sanwa and it's done.
Not sure why people are always advising Sanwa, there are so many other good brands....
To come back to the subject, yes there are center differences between brands, it is not always at 1.5ms pulse width but mostly it can differ from 1.48 to 1.52ms