i have solid discs on the back atm but i notice alot on ebay are vented

e.g.

http://cgi.ebay.co.uk/EBC-BRAKE-DISC...item335f141f62

Will these just replace the solid ones or do i need to go for the solid ones

http://cgi.ebay.co.uk/Brake-Discs-FO...item5d2c9b6536

thanks luke