You're not alone if you find yourself scratching your head when it comes time to comparing WSS vs MOSS Standard vs MOSS Enterprise. Often when we're in the design phase of some implementation and we're talking about leveraging a MOSS feature there always seems to be a pause while someone's asks: "Is that feature in WSS, or is it in MOSS? Is it only in MOSS Enterprise? Does the client have that?"
Luckily there's some relatively decent information that describes which features are available in which versions of SharePoint. Needless to say it's pretty important to know that the feature exists on the other side before you lob your solution over the wall.
I was surprised to find half decent Search in all versions although it does get better as you upgrade (you can supposedly index more content if you have hundreds of thousands of documents, have bigger content sources, index more types of files etc...). Enterprise most notably has the benefits of the Business Data Catalog, Info Path Forms Services, Excel Services and some other features that while are quite powerful seem a little niche to me. That could be because I'm a bit of a light weight in the BI space though.
If you do happen to get confused and wonder what it would cost a client to upgrade to various versions MOSS, Sahil Malik tries to explain MOSS costs for us in simpler speak than what you might find in a Microsoft brochure.
What surprised me the most were the costs for MOSS Enterprise, $57,670 plus $169 per CAL ($94 for Standard CAL + another $75 for an Enterprise CAL). For a lot of IT environments that 1000+ users that gets to be a SIGNIFICANT investment pretty quickly, never mind the hardware cost or the admin staff you need to keep on hand to manage a farm.
At least WSS is free (with Windows 2003) :-). I guess I'll start there and set aside a penny jar for the upgrade.