If you are working at lower frequencies for e.g. 10MHz, the CY2305C gives better jitter as compared to CY2305 (Standard Performance) and CY23EP05 (Enhanced performance)
The Enhanced performance is optimized for higher frequencies.
Check AN64360 - Device Selection in CY2305 and CY2309 Zero Delay Buffer Families application note that will help you choose the optimal one for your needs. The application note is available at:
http://www.cypress.com/?rID=46960
