Just a forewarning I am not a dietitian or a personal trainer but I played football for 16 years, including 4 at PLU and have taken 2 classes on exercise and diet, as well as read numerous resources given to me by the training and coaching staffs at PLU, along with personal research; and have switched off between early workouts (pre-6am) and late workouts (post-6pm) for extended periods of time over those 16 years. Now I am a web developer and have a good ol' 9-5. All of the sources I have come across have had very similar research on the topic and I will try to summarize and extrapolate for you, as well as indicate which is which.
Attempted Summary of Research:
When you are asleep your body goes into a hibernation like state, due to the low demand and long period of not consuming calories, thus your metabolism is greatly decreased. It does not naturally start up again until you have eaten, a sign to your body that it is ok to start burning the normal amount of calories because you have finally consumed some. This means that you will be more sluggish and underperforming your potential until you have "restarted" your metabolism with a meal.
When you workout you are adding a greater demand on your body's consumption of calories, for obvious reasons ranging from heart rate to O2 production/consumption to muscular calorie consumption, thus your metabolism is greatly increased, and it takes as long as a couple of hours after your workout for it to drop down to your resting rate. That is why you may have heard that you can get away with eating anything after your workout, your metabolism is burning in overdrive directly afterwards.
It is pretty obvious that proper hydration is vitally important to physical exercise to insure your body has a reserve of water to consume while exercising. Water is used in the body's natural cooling mechanisms, sweat for instance, your lungs consume water in the process of putting O2 into the bloodstream, which you are highly increasing the demand for when exercising, and water is consumed by the muscles during exercise (for instance; Creatine is an essential nutrient for skeletal muscle and brain function that can be found in many meat food sources, from salmon to steak, as well as created from a mixture of amino acids when not dietarily sufficiently supplied. Creatine is responsible for converting an energy source used in aerobic exercise (ADP) into its anaerobic cousin (ATP). In this process a lot of water is consumed. Which is why you may have heard of athletes who supplemented creatine and wound up with heat stroke and other injuries, they were not properly compensating their increased consumption of water).
Attempted Extrapolation of Research and Experience:
In order to properly workout in the morning you will need to go to bed earlier, insuring the proper amount of sleep, be hydrated when you do go to bed, and eat a small breakfast and drink a couple of large glasses of water right after you wake up, the earlier the better, to make sure you are hydrated and have your metabolism started with enough energy to get through your workout. Then after the workout you will have to eat a big meal and drink more water to help with the recovery of the workout, similar to what you probably do after your evening workouts now.
What I have noticed with working out in the morning is that it takes some getting use to. Not only is there a little more planning involved (going to bed earlier, hydrating before bed, getting a meal in before the workout and afterwards) but when you start, it will make you more tired during the day until your body gets use to it. I've noticed this lasting from 1-3 weeks, depending on how often you workout (the more often, the faster you acclimate to it but the worse it is at the beginning).
All that said, I love morning workouts, once you get use to them. When you are properly fed and hydrated before hand and have gotten past the acclimation period, you will feel more energy and most likely more joyful during the day, particularly in the mornings, due to the increased metabolism right afterwards and the endorphins released during your exercise. And the feeling of accomplishment that comes with a good workout is increased when it is early in the morning, probably due to the increased difficulty of getting up early. Also coming home from work and not having to get a workout in because you have already done it is a great feeling. All in all I would say that it is a good idea to give morning workouts the ol' college try. After a month of 2 you may discover that it is less fulfilling than it is difficult and then you will get your answer, but if you have a similar experience that I have, you will notice an increase in mood, energy, accomplishment, and satisfaction (after a week or 2 on the energy and possibly mood).