The MOXF has a built-in sequencer with both a linear SONG mode and cycling (looping) PATTERN mode. Both are ideal for drum track construction. In fact, there are some 7981 arpeggio phrases (more than 2300 of them are drum phrases). These have extensive real time control features that allow you to adjust the timing and feel of the phrases before you commit them to a track of the sequencer. Additionally you can create your own drum phrases and grooves directly to the tracks of the sequencer.

The PATTERN mode sequencer is designed like a drum machine (although it is not limited to just drums). There are Preset 72 Drum Kit Voices (32 User Drum Kit Voices). The arpeggio phrases can be used as is or can be transferred to the sequencer where you can edit the data. Your choice. The arps are designed to be recorded to the drum machine like sequencer. But you can assign any of the Drum Kits to play an arp while you play along with any of the sounds in the MOXF's huge (expandable) library of sounds.

The S90 XS/S70 XS while it also has arpeggio phrases, it does not have a sequencer into which you can record those arpeggio phrases.

You can read about the MOXF sequencer and its many Drum Track construction tools in the following articles (from the RESOURCE section here on YamahaSynth:

_ One Sequencer, Two Modes, Many Related Jobs
_ The Groove Grid - Play FX
_ Divide Drum Tracks
_ Real Time Loop Remix
_ Pattern Phrase - Pattern Patch
_ Rehearse and Erase Functions
_ Recording a Basic Drum Loop

None of this is available in the S-series. The S-series is basically a Motif without the recording sequencer. You can setup arpeggios to play along with in real time, but there is no recording capabilities, as found in the MOXF and Motif-series.