That's a good point that I considered; ultimately it's a tough comparison because I need to compare "popular" apps. A Windows twitter client that is super well designed but only has 2 users isn't a representative app (e.g. it's not reaching enough people to positively affect the Windows brand). QuickBooks, with 5+ million Windows installs is a super well-known app. The other accounting packages on Mac OSX are much less used.
However, you could use Xero, Harvest, or Freshbooks as examples of alternate accounting packages, and in my opinion all of them are better designed than QB.