Which is a better camera lens -- dcm or usm?

Question:

Which is a better camera lens -- dcm or usm?

My friend is an amateur photographer (and is taking courses to be semi-pro one day). I want to get a lens for her Canon EOS 30D camera for her birthday. Currently, she doesn't have a lens for landscape and wildlife. From the research I've done the EF 75-300mm f/4-5.6 looks appropriate, but it comes in 2 versions: DCM and USM. Which is better in terms of getting fantastic pictures? Thanks in advance! ~ Sincerely, Don't Know Much About Photography

Best Answer - Chosen by Asker: The USM version is more noiseless and focuses faster - it's better. But in fact 75-300 is not a good lens. It'll only disappoint her. Better take prime lens like 85/1.8 if you can spend 100$ more.