I prefer Coke Cola but I do enjoy a Pepsi from time to time.
Coke has a more smooth flavor while Pepsi has a bit more sweetness in it's taste.
Most people that prefer Coke like it because it isn't as sweet as Pepsi, if I drink Pepsi too much it makes me feel like I'm eating liquid candy, and to me that is not as enjoyable as it sounds.
Now if events are going on I grab the Pepsi first, sugar and excitment go together, hand in hand.
So technically it isn't a question of which is better, it is a question of do you like it a little sweet, or super sweet?