Exercising as soon as you get out of bed in the morning can be a great way of establishing a long-lasting healthy habit that you'll stick to. Later in the day, it's all too easy to be distracted by the many other things you need to get done. Getting up early and getting your workout out of the way may just work for you, especially if you're an early bird.
Night owls are unlikely to appreciate the early start and may need to find a time of day that fits better with their need for sleeping in later in the morning. In addition, because your body temperature is lower in the morning, if you choose to exercise then, you'll need to factor in extra time for a longer warmup.