Either one will do the job. Personally, I do not work in any genres that need multiband compression on the master bus, so I use neither. I do sometimes apply multiband compression for remedial treatment of vocal tracks, in which case the Sonitus Multiband does the job nicely.
(That is, until FabFilter decides to make a multiband compressor, at which time I will jump on that one in an instant! But alas, they do not offer one yet, so it's the Sonitus for now.)