I am seriously confused as some times people say you need to use an exact match domain where as other times other folks say that I should be looking for the shortest names possible.

Now I sort of get that names like Google, Amazon and even CNN are pretty short (well really short actually) but does that mean they are short therefore they are succesful for SEO or is it they throw millions of dollars in promoting them.

Lets say I had http://dogtrainingsecrets.com would that fare better in the search engines than http://dts.com (I haven't got either so this is very hypothetical)

Surely logic dictates the site with the keyword does better but if that was the case other sites would always rank below and I know that isn't true.

Has any one tried building a two sites and seeing which works best as I am starting to wonder if direct match domain names are as important as I thought especially when you start to add extra words to them such as in this case "secrets".

When does adding stuff to a domain name cease to make it exact match would say mydogtrainingsecrets.com be worse than dogtrainingsecrets.com or would they be in principle the same?