[jeffdavis]

"I'm more interested in knowing what PgSQL does better than MySQL today, in 2011."

The most striking difference[1] is probably the cost-based optimizer and the availability of a lot more execution plans. Most often cited is that MySQL has no hash join, but there are lots of plans that make a huge difference in execution time, and (for the most part), mysql just doesn't have those execution plans available.

And these are algorithmic differences. Typically, you think of optimization as something that does your same algorithm, just a little faster. In a SQL DBMS, optimization means choosing a better algorithm.

And it's hard for MySQL to add new algorithms because it doesn't have a cost-based optimizer, so it would have no idea which ones to choose.

[1] There are lots of other differences, but sometimes differences aren't easily represented as convincing "check-mark" features. So I really think you are asking the wrong question. The right question is: if I were making non-trivial application XYZ in postgres, how would it be done (from both dev and operational standpoint)? And is it easier to develop and smoother to operate if I do it that way?