Amycus was much more open about practising the Dark Arts and ready to actively hurt people on the slightest provocation.
Delores was far more subtle and devious, never openly supporting the Dark Arts and operating within the Ministry guidelines and in indeed Ministry support.
So yeah Amycus was worse at face value, and easier to stop. That's the part where Delores was worse- she did things 'by the book' and was far harder to counter.