Google AdSense Medium Rectangle vs. Large Rectangle ~ Which one is better?

Google keeps telling us that Medium Rectangle (300 x 250) is the best ad format among all. Do you agree with that? For the past 3 years of blogging, Large Rectangle (336×280) was the one that I placed on my blogs. Why? I read lot of websites state that it attracts more clicks which turn into more revenue. I believed in them blindly since Google AdSense is all about CPC, right?

Medium Rectangle (300 x 250) with 3 ads

Based on Google, “By opting all of your units into text and image ads, you are increasing the competition among the ads competing to appear on your site, as both test and rich media ads (image, flash, video and gadget) will compete in the same ad auction to appear on your site. Our system will always automatically display the ads which will yield the highest earnings for you.

Based on my experiment for past 2 weeks, Large Rectangle (336×280) does attract more click. But higher click rate does not mean that you will have higher return in revenue. Medium Rectangle (300 x 250) works better as advertisers prefer this format and competition increases the ads price. In return, I have higher Page eCPM with Medium Rectangle compare to Large Rectangle which have more clicks.

As I told before, never stop trying and testing Google AdSense until you get the best earning for you. Google AdSense does not perform the same on every website. Therefore, you need to find out the one that match your website. So far, I managed to find out that publishing both text and images ads are better. And Medium Rectangle is performing better than Large Rectangle in my case. How about yours?