Hi! I like to stitch by color, this is commonly known as cross country stitching, I stitch where ever the color takes me and for as long is I feel like stitching that color or until the next stitch is just to far away. The other method of stitching the area and "parking" your threads is just as good for some people. but I cant seem to keep all the threads organized. As far as which is faster i think all depends on you and what you are comfortable with, its just a matter of personal preference.
Obviously, I dont do this to the original pattern. But I make photo copies, and cut a small section of the pattern off, normally a 30x30 square section. I tape that to a piece of scrap paper, then I actually sew the scrap paper to my fabric. I use q-snap frames so its held taught. Then I pick a corner, start with that color, and do all of that color in the section. I go on to another color, and then around the whole pattern. I make fewer mistakes by eliminating how much counting has to be done.
oic... thats a good method... cos when you stitch 30x30, you will see quickly how the thread blending goes and when it looks cool, it will be encouraging to finish the work soon...:)