Before I learned that ColdFusion could reset the page buffer (either though the CFContent tag or through GetPageContext()) I used the CFSilent tag to cut down all pre-page processing white-space. Then, once I learned about clearing / resetting the page buffer, I started putting that in my header files right before the doctype definition.
Right now, I use both. All my pre-page processing is still in CFSilent tags AND I reset the buffer prior to page output. Just out of curiosity, I did a test to see if one had a performance difference over the other. As a test I did a TON of pre-page processing on a page that had CFSilent and also on a page that only had a CFContent tag reset the page buffer. As it turns out, there was absolutely no speed difference that I could see.
Good to know. Now I don't have to feel bad about using the combo of the two things. Even though I don't need CFSilent if I use the CFContent tag, it makes me feel more organized, like I knew that I needed to suppress output and did it intentionally. The CFContent tag just feels a bit sloppy, like I am worrying about white-space management as an after thought.