Which is more important: be holy as God has called or love others?

One should not preclude the other, but in reality this influences schools of thought and behaviours. Can one be holy and not love ("agape") others? And what is the basis of love without a longing for holiness (which is driven by love of God)?

Equally important is understanding the reason. Is it out of fear that God will punish or will not allow entrance into heaven? Or fear of humanity's end due to Christians failing to do them?

Doing it out of fear will not serve the purpose. Fear is not love.

“Love the Lord your God with all your heart and with all your soul and with all your mind.” “Love your neighbour as yourself.” (Matthew 22.37,39 NIV)

Only when the reason is Christ' love, can I both love God and love my neighbour together.