I have Keynote, Numbers and Pages, and DocsToGo and QuickOffice HD.
I tested all three apps (Office Suites) and found Keynote and Pages much better for what I need to do.
As far as Numbers is concerned, I rarely use it or the DTG or Quickoffice equivalent.
But - as always - it heavily depends on what you want to accomplish.
My ranking:
1. Apple Suite
2. QuickOffice HD
3. DTG
As you already tested DocsToGo and the Apple suite - do you have found your favorite app from those two?
Hope this helps a bit.
Knut