Better is relative. Each has it's benefits to you ... asking which is better is like asking if broccoli or spinach is better for you.
They're both good, but for different reasons.
Read the nutrition label on the boxes the next time you're at the grocery store and see what you think and what works better for you. If you like the Multi-Grain better, then eat those. Either way, whole wheat or multi-grain is a better choice than regular white pasta.
Edited: Ok, so I did a little research for you (cause I'm a geek).
Barilla Plus Multigrain: semolina, grain & legume flower blend (lentils, chick peas, oats, spelt, barley, egg whites, ground flaxseeds and wheat fiber), niacin, ferrous lactate (iron), thiamine mononitrate, riboflavin, and folic acid.
Barilla WholeGrain: Whole Durum Wheat Flour, Semolina, Durum Wheat Flour, Oat Fiber.
So you can see the big difference in the Barilla brand (which is what I buy) is that the whole grain is wheat, semolina, and oat. The multi-grain is semolina, lentils, chickpeas, oats, spelt, barley, wheat, and flax.
I personally would choose the Multi-grain for the benefits of all the variety, but there's nothing wrong with the whole grain either.