They both are really nice, bitdefender has better real time protection in their free version than kaspersky. But kaspersky has really amazing stuff in the pro version. So it all depends on if you plan on just using free or going pro. I find kaspersky has better internet security than any other anti virus that I have seen, but bit denfender is also fairly strong. Kaspersky and F-Secure I think are the few antivirus companies atm that will include govermental malware in there scans and remove it. So I would go with kaspersky