Which wing of an airplane is more important? Obviously both are equally necessary and therefore both are equally important.
Which is more important: what we believe about God or what kind of life we live? Again, both are equally necessary, and therefore both equally important.
In fact, the Bible says that if we claim to believe in Christ but it doesn't make any difference the way we live, then our faith isn't really genuine. This doesn't mean we must be perfect... but it warn us about the dangers of a shallow belief in Christ that isn't honest or real.
" What good is it, my brothers, if a man claims to have faith but has not deeds? ...Faithby itself, if it is not accompanied by action, is dead."- James 2:14,17