Ramp Test vs 20 Minute FTP Test vs 8 Minute FTP Test

How bad would it be if I alternate between ramp and 20 min test.

Ive been challenge by a friend to not be a wuss and hit a 20 minute test.
He thinks the 20 min is more accurate for a person like me (a triathlete).

Since i started on TR ive only done ramp and it has work for me. Not sure how would i react if my power jumps too high or too low after a 20 min test