From what I've picked up, Tobi appears to be more balanced of a character due to his Unyielding and his chance to dodge. On the other hand, Sakon/Ukon are pure offensive, damage types.

Tobi's more balanced nature might be better than Sakon/Ukon (I've never tried to compare) but I personally prefer Sakon and Ukon just because of the solid damage output, defense debuff, and self-sustainability with the lightning Leech (see Dosu's post if you don't know what I'm referring to...I tried it and it's pretty good)