The only issue with side by side cutting and using the kerf blade to split the difference on the glue line is when you have a variance of heights between the two. Also it might be harder to clamp off both boards and keep them from moving. I think erock's method that is shown is more straight forward. I would think both would work and on sheet goods with equal heights it's a toss up. On dimensional lumber I would choose to stack and cut on a bookmarked cut?