It’s a 2 part blog post on the different technologies for disk imaging…good read.

http://blogs.technet.com/b/stephenrose/archive/2010/07/17/improving-your-image-sector-based-file-based-and-sysprep-what-makes-the-most-sense-part-1-terms-and-windows-tools-primer.aspx

http://blogs.technet.com/b/stephenrose/archive/2010/08/12/improving-your-image-sector-based-file-based-and-sysprep-what-makes-the-most-sense-part-2-the-pros-and-cons.aspx