Both have their drawbacks, but overall Percona is perfect for Magento. What do you think? There's a load of useful server tips here about Magento.
I prefer Percona. What more would you like to know?
MySQL work well for me. I guess there are more and more vendors who are MySQL compatibile, so there's more choice. Generally, no matter the DBMS, you should think about optimizing your configuration and schema.
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