Mesomorph contains 350mg of caffeine per serving. That's the same as 4 cups of coffee. That is a lot of caffeine to take in one sitting. It's going to rev you up and get you wired but it won't actually improve your workout.
Of the two, I would pick creatine. Creatine is very inexpensive but a very effective product. Creatine is one of the few supplements that has literally hundreds of human clinical studies backing it's effectiveness and safety in humans.