I've always used OEM blades on my Cubs Cadets and on my commercial John Deere Z-Trac and Toro. These are getting very pricey so last fall I purchased Oregon Gator and regular blades for all 4 of my mowers. This coming summer I'll find out if they can preform and last like OEM blades.
http://www.oregonchain.com/pro/pro_home.htm