This is a common question. What you can count on, statistics never matching from one product to another. They should be 85% to 90%, but each product will interput things different. What is important is that you compare history within one product, not from one product to another. What you should see also, are simliar trends in both products but with different values.
Also, not sure if your talking about the Web trends (log analysis) product or the JavaScript version. A JavaScript product will be completly different from a log analysis product.
Hope this helps,