The MODX (and the Montage) originally didn't have a sequencer, per se. More like a way to record ideas. They added a Pattern sequencer with an OS update, but it's still not a full sequencer, which doesn't bother me, as it's one thing in the MODX that I never use.
Of the three instruments mentioned in the original post, I prefer the Krome's sequencer. Unlike the MODX, you can overdub parts, edit them afterwards, and the touchscreen (which is an advantage over the FA) makes that pretty easy to do.