npn vs pnp diff. amp

to all the guys & gals out there hello,

i have seen lots of schems on audio electronics using diff. amps as input stage. i have noticed that majority of diff. amp used are npn. my question is "is there a definite advantage if npn are used, if there is what is it.

i have done some research but could not find any explanation on whats the advantage or disadvantage. or maybe i just did not see or understand some of the explantion.

thanx.