Mokona also had a more important role in the manga due to the crossover with TRC. Since all of those crossovers were cut out for the anime, Mokona was left in as a cute mascot...in a series that didn't need a cute mascot.

The white Mokona (Soel) was a much better character than the black one (Larg) in the end, though -- I think Larg was ultimately reduced to arm decoration in the last chapters.