I'm happy to have the B3 on my board to mostly handle flange, chorus, delay, octave & filter. They're the effects that I don't really need too often and I can't justify spending a shed load of cash on the separate pedals. Or having a massive board, unpractical for most gigs, half filled with gear that doesn't get used a lot. But I love my overdrives and distortions. These I do use, a lot. And I have 5 of the real thing on my board. For me, I have the best of both worlds and I'm happy with it for now.
Definitely a case of each to his/her own here, but I'm struggling to imagine how an old digital multi fx unit can try to sound remotely useable next to the new breed of digital kit, like Line6, Zoom, Boss etc.