Trend Micro offers a 30 day free trial. After that, you have to subscribe. I have been using Trend Micro Maximum Security here for over a year now. I trust it, as it has found things that came in via flash ads and things like that. And not only did it find them, it stopped them before they did anything. It has all kinds of features to it. I do not even use all of them. But I do like how my system performs with it running.
I have never run Avast, so I cannot compare the two products.