Both units will serve a similar purpose, namely to redirect enemies. The more expensive one will also serve as chaff hunters and potential flankers, as they can still be fielded with 7 squigs in the front row and 3 herders in the back. The downside is that if a nasty unit charges in and kills off all of the squigs, the unit will not go wild to inflict the additional D6 S5 hits upon panicking. The cheap option, on the other hand, will be unlikely to kill anything, as you will most likely run them with only goblins in the front rank, but they will inflict the Go Wild effect on the enemy that killed them (who will have problems killing the Squigs in the back row before combat is over).
Compare that unit to the ever popular single Trolls running around, and you will exchange stupidity for animosity, which depending on the situation might be preferable. The Troll, however, will be faster and more mobile with pivots, which may or may not be useful in some matchups. They can also be surprisingly effective as a flank harasser, since T4 3 wounds with regeneration can be frustrating to kill off with less than a rank of fighters engaged with it. In the end, I think either choice is viable and either one can be more effective depending on your playstyle. The best thing about all of them, however, is that they're very cheap and if you're going for a heavy diverting army, you can easily fit all of them in your list.
