I think you may be right about the MS-60B+ !
Compared to the B1-4:
- the MS-60B+ has got 6 slots per patch (one more than the B1-4), 100 patch memories (vs 50 on the B1-4); better processor & upgraded sims, ability to send a split signal to PA (e.g. with cab sim) and to amp (e.g. with no cab sim), more compact form factor;
- the B1-4 has drum machine, basic looper, headphone capability, aux in and ability to edit using PC compatible software - all features I make use of and would miss. On top of all that it's ridiculously good value.