The corrosive qualities depend upon the concentration of the acids, and the substance they are in contact with. Concentrated hydrochloric acid can be considered the more dangerous as it can fume, and inhalation of the fumes can cause serious injury.
Hydrochloric acid has a pungent odour, and is a clear, or slightly yellow, watery looking liquid. Sulphuric acid is also clear, but has a distinctly oily appearance if you swirl some in a glass jar.