Girl4, not to quibble on small minutia, but, actually, on KOTB, we see exactly what his strengths and his weaknesses are. When he tries to sing in a higher register, it's weak. It's effective on some songs, but not on others. However, when he sings in the lower register ("My Valentine," "Ac-Cent-Tchu-Ate The Positive," "Get Yourself Another Fool"), he nails it.
All told, he probably sings in the higher register MORE on KOTB than not...but, the voice is definitely stronger, more in control, richer when he sings lower.
in years to come/they may discover/what the air we breathe and the life we lead are all about/but it won't be soon enough for me