The extent to which adult cats enjoy each others' company is largely a function of how they were socialized with people (and/or other pet cats) as kittens. When we adopt them as kittens, we actually get them partially stuck in kittenhood in their socialization. Those tend to be the ones that sleep together, wash each other/accept the other's washing attention, and play together. So this may be a factor in deciding on either kitten or an adult cat as a newcomer; unless of course the adult has been kittenized elsewhere.

~Susan