Which anti virus should be my main one? avast or mse?

avast or microsoft security essentials? which one should be running in the background? at the moment they’re both running in the background. I also have malewarebytes and superantispyware running in the background, with spywareblaster and spybot search and destroy idle and comodo firewall. Are any of the above useless because I’ve seen some good reviews [...] http://bit.ly/piPP7R