I don't have it on my tablet because the tablet runs worse than it does now compared to my phablet. Cheap tablet yanno. The best antivirus however is a subjective thing. Try them out and use the one you like the most. Don't be afraid to switch. For example I used Lookout for a long time but switched to Avast earlier this year. Both work well but Lookout started treating apps I modified using a test key as malware, wanting me to remove them. Avast doesn't do that, so I switched.
If you feel you need one, there are several free anti-malware apps available on the markets. I'm using AVG on mine with no apparent performance issues.