Urgent: XI 3.0 vs XI 7.0

Hey,

I'm planning to attend the TechEd by this year and I do want to write the exam on XI 7.0 is also.

Can Anybody tell me what is the difference between XI 3.0 Vs XI 7.0 versions??!

And the what would be the expected questions from XI 7.0 Version?!!

Do the needful.

Cheers.,

Stallin