I've owned both, and as a 'multi' FX I'd go for the b3. On the ms60b, you can set up patches and you can switch between them but it's not the most flexible of process. However, I use the ms60b every gig I play. As I basically have but setup as Octaver > noise reduction > compressor > preamp. I have it sitting on the octaver so it's switchable on and off, and the others are always on. Plus it's my tuner. For me, it works brilliantly but I can see the limitations won't suit everyone.