I had success with PicoSure removing a black tattoo. Should I stick to it or will PicoWay be better for another black tattoo?

You can use either. Black inks are often combinations of many colors of ink, so that's why some lasers work better than others. PicoWay does better with blue and green inks so if you find that when you're getting your PicoSure treatments that there's a lot of blue and green remaining inks, then I'd suggest using a PicoWay device. "This answer has been solicited without seeing this patient and cannot be held as true medical advice, but only opinion. Seek in-person treatment with a trained medical professional for appropriate care."