I would stay away from AVG to be honest. AVG have a poor detection rate in my opinion, is buggy, causes a lot of Windows related issues (slowness included) and it comes bundled with a spyware (their AVG SecureSearch Toolbar, look it up). Also, AVG PC Tune Up is one of the worst piece of software there is. The only way it actually increase your system performance, is when you uninstall it. Not even joking.
tl;dr version : Stay away from AVG products, they aren't worth it at all. Also, Bitdefender is good, the only issue is that it's an heavy resources consumption Antivirus in my opinion. I would rather pay for a Kaspersky or a ESET product (ESET if you want to keep your resources, their products uses around 200-300MBs less RAM than Kaspersky's products).
But that's just my opinion.
I've had a GREAT experience with the new
Bitdefender Free 2014, installed onto a 2.0 GHZ - 512KB RAM, it runs smoothest of any that I tried, about 5 different AV attempts on 512 RAM this one makes
MSE seem sluggish and heavy in comparison. I'm so impressed that I will probably write a little review on it, because not many think positive of Bitdefender free edition. It's an install and forget type anti-virus. Good AV for basic-medium users like myself.
So far, the only competition I found on "lowest resorces" for free is
Unthreat (Viper Engine) which is maybe even lighter, but has errors trying to update the definitions, it stalls out for some reason.
I haven't figured why people like
AVG so much... its not the best protection and it doesn't function very well... it might be fine at first, but when I tried to update it failed. It didn't like the slow connection, but other anti-virus handled a slower net connection just fine. This was on a PC and Laptop with 2GB RAM, and 1GB.
AVG was already installed on laptop, the boot time was looong, and it was buggy wouldn't update and error messages just trying to use it. Experts only apply, because I couldn't figure out what was wrong.
Replaced it with
Avira, now it's doing better, without errors or fuss.