I use both and I track the traffic comming to my site. Internal blogs are read 3-4 times daily. The external blog I use bring 18-20 hits daily. Obviously the external blog I use coms from a PR8 where as my site is a PR4. But a lot of it is content that brings the readers. I have seen blogs from my site on MSN but none on Yahoo or Google. External blog appears on all 3. I suugest using both it can't hurt. You can post the same content just rewrite it then it is fresh.

PS Training camp starts in 1 1/2 weeks do the Browns have a chance this year?