They can be more aggressive, and they can be very docile, once again dependant on the particular individual. The one I had was one of the most homicidal maniacs I have seen. The list of fish killed by him were pretty strange, and pretty tough.
there are a number of species of bristlenose plecos, two males together is asking for trouble- certain death, but you can keep em with several females. i've never kept them with other plecos