the beef may taste far superior from Angus and Hereford bulls, but the carcass size and shape is far far superior from the contenintals, the markets/abbatoirs pay more for a bigger/better carcass and therefore dictate almost, what breed of animal many farmers breed.
what size are the cows? if they are big, well grown things a charolais or even a BB may be an option.
if they are quiet cows you could use a lim bull and the calves should not be too much of a problem- but i suppose you could get the odd mad one!
to a certain degree, where you live and what system your cows are on could affect your choice of bull- we find contentntal types are more 'nesh' than natives, they dont 'do' as well off hard land.