The word Mahabbah (Allah's love) is only and most befitting of Allah.His love when bestowed upon the ' chosen one' (Khawass),settled in the soul and began to emanate from the one,as light emanates from the sun.Its beautiful fragrance would attract the people to him and make them love him.This occurs when Allah loves oneself.
As for the word Hubb (seed from Habba) is more widely used in mankind. When human shows love to one another, it does not penetrate the beloved,such that others then begin to love them also.  So, it was only right to use different words to express these different types of love.

(When Allah sees His love in AHMAD ,it is His Mahabbah in the 'Meem'. Planted in Adam,  is the seed (Hubb) from Habba, but the holy spirit of "Meem'(Mahabbah) in AHMAD is kept secret deep in the heart and soul.It is our duty to purify our heart and make our intention and wish sincere, just for the sake of Allah.That Holy Spirit (AHMAD),is the only One who knows the true path to Allah and may he guides us to Him.)