Most people have a solid preference for which type of energy bar they like to use. Some people are Clif, some are Powerbar, some like Luna, and some people can't palate any of the stuff and just use bananas and raisins.
Personally I find it easier to carry an energy bar, instead of a pound of bananas, a box of raisins and a bag of apricots. I find Clif bars to be a very good option in this realm. Several of the Clif bar flavors actually taste good and have a texture NOT reminescent of stale, dried, lumpy oatmeal. Totally a good thing. Clif bars pack a good wad of energy, from a mix of immediately available sources as well as substances that will provide energy more slowly for sustained output, keeping your wheels churning.
For a long time I used only Clif bars because I really didn't like Powerbars. But after a few seasons of cycling and learning more about how my body likes to work, I actually use both. I find that different conditions lend themselves to different food sources. If I am riding in colder weather or doing a long slow day of training, I find that Clif bars are ideal. Their sustained stable output keeps me energized to stay warm or to go the distance without lots of stops to fuel up. But they can be too heavy for hot, humid conditions or high intensity maximal effort type rides. In these instances, I prefer the lighter Powerbars. They melt and turn into energy very quickly and burn off quickly as well. You don't get that heavy feeling that can make you sluggish on faster paced , higher intensity rides.
Beyond performance, Clif bars are made from mostly organic ingredients which is important for those who like to watch what they put in their bodies. Also, Clif uses recycled material for their packaging which is environmentally friendly. A nice touch to impress a bunch of crazy outdoorsy type people...