Yes, it's very true, there are different coat types, we're talking show types here..(not working types)
here is my --strictly personal opinion!
-- blacks and black and tans are the hardest, their coats can get very (very!) thick and wooly. Red/golden can be difficult, but have so much variation in the amount of coat they grow, the breeder can advise about how much coat their dogs grow.
As far as the partis go, the black and whites are the hardest, the more white on them the more difficult, as the white tends to get wooly and sometimes hard to keep white. (but again, sometimes the white can be more coarse than wooly so that makes it al lot easier)
Blue roans and orange/lemon/golden roans tend to be the easiest IMO, but again there is a wide variation.
Sorry, don't have enough experience with liver or liver roans to comment.
That said, I wouldn't make it the basis for my decision--if I fell in love with a thick coated black, then I just know I'm going to spend a lot of time grooming!