is there a greater benefit in taking supplement vitamins in the morning?

Some vitamins are best taken with food. In particular, fat-soluble vitamins (like Vitamin D) are better absorbed with a meal. In other cases, certain vitamins (like iron) can inhibit the absorption of others, so taking it with food helps dilute everything and allow for better absorption. Based on all this, the best thing to do is to take your vitamins with a meal. Most people eat lunch away from home, so the most convenient time to take them is with breakfast or dinner - either is fine.

Lastly, there are a few vitamins (some of the B vitamins in particular) that have a mild pick-me-up effect. This effect is not nearly as strong as caffeine, but it might be a good reason to take them in the morning instead of at night. Magnesium, on the other hand, helps with sleep. This is the one vitamin that I know that is best to take before bed. In both cases, the affects are slight, so if you are taking a multi-vitamin you can probably get away with downing it any time of the day.