You'll get the best response to your articles at the 450 word mark, according to my testing. You need at least 300 words to keep the reader's interest, but at 600 and above they tend to get bored and click away. 450 splits the difference pretty nicely.
What is the overall end goal of article marketing? Is it to build backlinks to your site? or is it to get quick traffic and earn money from affiliate products via the links? I always thought that it was best to provide quality articles that would appeal to webmasters with good websites and get highly quality backlinks?
Make it rank higher in ezinearticles, thats the key to success. They rank on basis of views, send visitors/viewers to your article. Looking forward to your next update