Mmm personally, I have the bone, MF chenille mitt, chenille sponge, synthetic wool pad, actual wool pad, sheepskin glove, LC blue grout sponge, but in all honesty, I didn't understand why people loved those home depot grout sponges, but after using them I can't go back (unless it's a super dirty car like in the winter or something then I bust out the MF or sheepskin).
They work well, release alot of ONR, capture dirt without marring, they're CHEAP AS HELL (less than $2 each), don't stain that easily, they're soft, and best of all, if I cut them into cubes like the LC blue grout sponge, it works even better at capturing dirt without having a chance to scratch the paint.
But keep in mind this is only for ONR, I'd never use them with a traditional wash; the other things are just so much better in that regard.