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Yep, I've found the two to be interchangable. However, I would note that while I've always been a big fan of Sugar in the Raw, I only use it now for long smokes (like Boston Butts). The last few times I used dark brown sugar for my rubs and found that I got a better crust.
If you want equal measurements, you need to use weight instead of volume. Find out how much .25 cups of brown sugar weighs and them use the same amount of Turbinado or white.