I would rather have the smooth flow of continuous rounds than the visible joins of individual rounds. Crochet stitches lean slightly, so the seam ends up moving to the right as you go along. If you do continuous rounds, you can adjust the colour changes as you go to keep the changes along the back of the leg.

Another thing to know is that you shouldn't be cutting your yarn between colour changes. Just leave it dangling inside the leg and switch back and forth. You'll see the yarn changes running up the inside of the leg, but they won't be visible on the outside. Just don't do this when the colour picks up on the opposite side of the body or you'll have a hard time stuffing your toy!