I recorded a band some time ago whose guitarist used one with a no name transistor amp. Although the band wasn´t into metal but more into alternative/rock the Engl blew me away.
I tested the high gain sounds just for a few minutes and it was absolutely amazing. If I had the money I´d buy one instantly. It is much better than a rectifier in my opinion (and I own one).
I don´t know the powerball cause I never tested it but I recorded a Savage 60 and a Savage 120 and the Engl is absolutely equivalent if not better because it has more sound options.