I am preparing a presentation for the Longhorn PHP conference titled PHP & MySQL -- How do PDO, MySQLi, and X DevAPI do what they do. This will be a comparison of using PHP with different MySQL Connectors. As far as I can tell there are no three way comparisons of mysqli, PDO, and the X DevAPI PECL extension. And much of the PDO versus myqli stuff looks to me like it has not aged well.
I have good material in the raw presentation about overall features, parameters for prepared queries. And a good section on the how's and whys on prepared queries.
But what else would you like to see in such a presentation? I have read some postings on the web about turning off buffering (fairly simple to do). But what else are would you like to see compared?