Worst AV ever: AVG Free Edition (Required License, All over the place, crashing, ads)
Runner-Up Worst AV ever: Microsoft Security Essentials
3rd Worst AV ever: Kaspersky (UI issues, lags, freezing)
Then Avira, Emsisoft, Avast, and Bitdefender/ESET, notice a pattern?
Bitdefender is quite lightweight on my computer now suddenly! It deserves a ranking on my top 5.
Chromatinfish, I think I know now what you experienced with Kaspersky. I remember when I first tried it, Kaspersky is freezing its own UI, slow at boot, and lags. I believe that the earlier builds of Kaspersky 2014 were the culprits - Kaspersky 2014 a and b. I believe they are fixed on c and later builds because I installed them and no issues were encountered.
I do NOT consider detection rate to be an important factor when choosing any AV. The detection rate is based on how the user responds to threats, it has very little to do with the AV in general. Just because an AV doesn't detect a malware sample doesn't mean that user will run that sample on their system.
Since no AV's can protect reckless users who don't try to learn or care about keeping their system safe, I only recommend AV's according the the following qualifications:
1. System and software compatibility. (if the product interferes with Windows components or trusted software, it is not worth using).
2. System stability (response time or how much they slow down the system, RAM is not considered to be accounted since it means very little on newer systems)
3. Problems, issues or bugs. (these can be so bad that the best features of the product are not worth using examples; crashes, BSOD, corrupted Windows components, etc.)
4. User-friendly (if a product is too complicated for basic users to understand then it is not worth using)
5. False positive detections (false positive detections can be more wost than most malware infections, infections can be removed but trusted Windows components, drivers, services, etc. get corrupted by false positive detection it usually requires full reinstall of Windows).
False positive detection also hurt software developers and destroy their reputation.
I don't recommend paid AV's because users can get infected just as easily using them compared to just using free AV's.
Based on my qualifications here is the AV's that are my Top 5 in order.
1. Microsoft Security Essentials or Windows Defender on Win8.
2. Avast Free
3. Avira Free
4. Panda Cloud Free
5. AVG Free