My last C230 was black and keeping it clean was no different, I washed it at the same frequency as my pewter silver C230 that replaced it. The biggest issue for me was the swirls, you can see them a mile away and people comment on them, that's how bad it is. Sure, you can polish and wax the car at least once a month, hand wash using the 2 bucket method and being very carefull but it's inevitable. Now with the new nano paint it should be a lot better than my 2002 as my 2004.5 hardly has swirls, even after a year.
But in terms of looks, nothing has the depth and shine of black car, even dirty it will outshine my silver car. The downside of black is that it's less visible at night so there's a higher risk of accident, on the plus side is also less visible to law enforcment. Besides, a black car in AZ, that's fantastic, very rare.