I've used them all with no problems, and have been using AVG for the last few years... some comparos have shown Avast to be a bit better.
I plan to get my 15 yr old niece a new computer for her birthday and I was going to build one but I was looking at the Vostro desktops and I can get one of those cheaper than a build. For her needs, surfing the net and doing homework, the Vostro 200 Economy for about $350 shipped should be fine. Glad I stumbled across this thread. Harold