I understand that there is specific IBU for all the beers....but what gives the kinda bitter (sometimes even unpleasant....compared to more aromatic india pale ales) flavour to some bitter ales?
Is it the hops? I mean it must be.....but for instance the IBU of an india pale ale and a bitter ale...sometimes can be similar, but the tastes are soooo damn different. I guess it is simply the hop-selection. If yes, then what hops do people normally use in bitters and use in india pale ales?
NOTE: it seems to be that the answer is that these beers are cask-aged/conditioned. That gives them that distinct, interesting flavour.