I had this same problem when I started my system. Except I was concerned with using Outlook (necessary for work) for my @Home private stuff.

I would suggest using Outlook as your priamary tool for the following reasons:
1. The Outlook Add-in has a 30 day trial which you'll probably fall in love with if you give yourself the time to learn how to use it. It's not that it's hard to use --- it just takes a few new habits (just like GTD...)
2. Outlook will be able handle everything that comes your way (or at least it does for me) --- Email, Calendar, Notes --- it does it all.
3. Many people use outlook so there is lots of support and places to find answers to your questions.
4. If you have a palm or blackberry --- the mobile synch capabilities rock! I use a BlackBerry with the NextAction! program. I love it.

I'm just happy that my system is all set up --- now I just need to concentrate on my GTD habits.

Good luck!

Ryan