I wish I could give you a straight answer, but honestly depends on your material setup , the texture size, and how much manipulation you are attempting to do. In general, math is cheap for the computer, and textures can be costly, but if you are doing a lot of math to get the ultimate results you are looking for that would be a single texture call it might be worth the additional texture. Also it is worth noting that you can open a material function up by double clicking the node so you can see exactly what that node is doing, more may be happening in there than you think …