Hi chelyw,
Personaly, I would rather drive a bus than a car around both of those two cities, but that is because i know them quite well. As far as parking goes, well a car is lot more versatile. Both cities have excellent (well in nz terms anyway) public transport which I believe would be your best option. Park where you can on the outskirts of the area of interest, then take public transport or even a taxi. It would be much easier on your nerves.
ps
I do not know what your capability is or familiarity is in driving larger vehicles.