The fundamental difference is that FSC develops the standard on an ecosystem basis. For example, the boreal forest or the Great Lakes and St. Lawrence forests in southern Ontario and Quebec is a multi-stakeholder standard. You end up with industry, aboriginal groups, environmental groups, and labour. They get together and develop a standard around how logging will look on the ground. That is the basis by which certification is done. That's imposed from the outside.
The SFI and the CSA, which were both developed in response to the emergence of FSC as a certification system developed by industry, led by industry--those systems operate like an ISO standard. It's a management planning standard. The company chooses objectives they want to meet and then they monitor their own progress against meeting those standards. Whether those standards have been met is independently verified on the outside, unlike FSC, which has a broad community-based standard, in that all the participants involved set the standard, and that's what compliance is measured against.
Also, FSC has chain of custody, which means there's a label on the product that ends up in the marketplace. I think most importantly from an economic perspective is that FSC confers economic benefits to the companies that are certified, whereas the other two standards don't because of lack of recognition of their standards in the marketplace. The reason it gets more money in the marketplace is that the original basis is more rigorous, so not surprisingly you're going to get an economic benefit for something that is demonstrating performance.