I prefer them in different instances. I can enjoy Pepsi at any point - the sweetness lets me sip it and enjoy it whether or not I'm particularly thirsty or feel a particular desire for something sweet. While with coke I tend to need to be thirsty or really have an urge for something sweet to enjoy it, but in that situation I tend to prefer it. I'll chug Coke but sip Pepsi. It's very possible that's down to brand presentation - e.g. the Coke association to the "bottle opening sound" is very real - their marketing is so extremely ingrained in modern culture.