Hey, I was looking under "abilities" for my party and scanning the percentages for how much they've learned for each dressphere...and I was wondering what is the most feasable way to level them up?

I've pretty much kept Yuna as the main gunner, Rikku as thief, etc...but now I'm wondering as to whether I should designate the other spheres to one character like I did with their original ones...or is it really worth having them each master all the dresspheres?