I think modular system when I think of using a PC / Mac solution. FL is my pattern sequencer. It's editing facilities and features are far ahead of the Motif's pattern sequencer. If you don't plan on working with patterns, than a regular DAW / Sequencer app might be better for you.

I often open FL in Sonar, because the audio recording / editing facilities are deeper. Still, one can produce and entire song in FL, as it supports multi tracks and effects. I like using a linear track sequencer like Sonar for it's audio faders and controllers. A guitarist I know has FL as well, but only has Cakewalk Music Creator, which is the entry level version and is very inexpensive, and FL opens an works fine in that too.

The Motif ES is an excellent workstation, but it's also WYSIWYG. If what's in it works for you, then it's a great tool.

AJ