Crumbled is easire to use, but it's also more expensive, considering it's very easy to crumble it yourself. Once it's crumbled, the manufacturer doesn't store it in the brine water any longer. Something in that water keeps it fresher, longer.
I buy a good size chunk, break off what I need, and keep the rest in a covered container, filled with the original liquid. I do change the liquid, replacing it with plain water every week. I've got a good size piece that shows no signs of spoilage in the fridge for 2 months.