Allow me to just point out that from a knowledge generating point of view this question is a settled issue…
Testing pocket holes against mortise and tenon and dowel joints
Dovetail vs. box joint strength
@frank_lima: no way. Both of these are inferior.
http://www.msitesting.com/images/Fillet-Weld-sample.jpg
Now that’s how to join something at right angles. 
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Just a comment on woodgears.ca’s tests based on the woodshop classes I took in the '60s. For a grade, we had to make a glued butt joint. If the joint failed at the glue, you failed. If the wood failed and the glue joint was intact, you passed. The point was, a properly made glue joint is stronger than the wood it joins. Since some of his joints failed at the glue joint, I suspect his joints, in those cases, were not well made.
I found his testing very interesting and informative.
Thanks for the post.