Regular Coke has a really strange after taste, not to mention terrible if you you forget about it and it's flat. Dr.Pepper doesn't have that odd after taste and still tastes somewhat drinkable when flat, so my vote goes for Dr.Pepper.
Like, it seems like I tasted it long before the first time I tried it.
I remember a blind taste test between Coke Pepsi and RC Cola. In most cases people were unable to tell the difference, even those who claimed they could often failed.
Tips about Coke (i'm not talking about how it's been made and from what, think you all know or heard about it... if no... dissolve 338 gramm of sugar in a glass of water and try it, sweetness is the same as coke have): - one glass of coce with 4 spoons of coffee makes really great effect (you can drinking it and after 30 minutes electrocardiography shows you have arrhythmia) - you all know the joke with mentos and coke - it's great dental raid remover (removes also enamel) - if you put some ants (for example) in a glass with coke and leave it for a while, you'll see that ants were eroded
This list may be endless. Almost the same tips may be wrote about Dr.Pepper.