It's not about which one is best but which one meets your needs. Since you already have iWork, how is that working out for you? Have you had any cross-compatibility issues with any of your Office documents? Features you need that are missing in iWork? If not, you're probably not a power user and therefore don't need Office.
You can save Pages/Number/Keynote file in Windows format e.g. .ppt or .doc so it works in Office too. Some features like Keynotes 3D effects don't work so you need to do quite simple stuff. This is what I do. I don't have Office but I've returned dozens of projects and essays and they have been fully compatible with Office.I write word docs, and the most I would use Excel/Numbers for would be home finances. When I go back to college though I'm sure I will use Pages more, and Keynote, those work fine with Office on another machine PC or Mac right?
I was about to say something similar.If you don't know about OpenOffice, you should check it out at http://www.openoffice.org . Its equal to any office suite out there today, runs the same on all popular platforms, and is free.
Highly recommend it! We've switched over at work and there's a bit of a learning curve fro the legacy (MS Office) programs, but once you make the jump there's no looking back.
Just to throw this out there... I use Keynote pretty much exclusively for workplace presentations. Usually, I bring my MacBook with me. However, just in case, I have Keynote convert the presentation to DVD as a backup. That way, if I am forced to use an alternate machine - Windows, Linux, or whatever, I have a backup that still has all my transitions the way I want them. Slides move forward and stop with the Chapter Forward button.Also, I don't trust Keynote conversions to Powerpoint format - many times I give a talk and have to use the host's computer, which is invariably a PC. Using a converted Keynote and hoping for the best is not an option. Furthermore, all the pretty niceties of Keynote are (apparently) lost in most conversions.
I like the mac versions better. Unfortunately, I work in the business/professional world where everything is MS office.......