PostgreSQL vs mySQL, any performance difference for large queries?

I need a database capable of storing at least 12 million records per
table, mostly used for batch queries. Basically an invoice database.
Some tables could potentially store 100 million records.

mySQL5 contains many of the features or PostgreSQL, and I doubt that I
need all these features. Are there any spefic benefits in query
performance or reliability of going with PostgreSQL?

Secondary need is a database where 200 users will need to perform
lookups, probably using Windows PC's. Most likely only a handful will
perform lookups simultanously.