I recently acquired an i7 920 from my brother, and it came with a coolermaster V8 that he had been using with it. That works fine, however it interferes with putting the side back on my Antec 900 case. I really don't overclock so I don't need anything too extreme, but I'd like something that does a good job in a moderate price range (say $30-50?) while allowing me to put the sides back on my computer.
There's not a whole lot of difference between the two and you could easily choose either one and have a very good cpu cooler. The Evo has a slightly higher cfm and a lower dba but also a slightly higher dba also. At Newegg the Evo is $6 more however at Amazon.com the Evo is $27.99.