Sintered base is a must on a pow board. Only time I would say it doesn't matter is for a beginner that won't notice the difference and on park boards that are going to get destroyed anyways.
I say the opposite, sort of. I say it's not a must. If the board is cheaper than a sintered one then sure, go for it. Don't let it stop your purchase. I just don't like extruded bases on expensive lib techs.
I had a first year capita charlie slasher, which has an extruded base...and it rode fine in powder.