By far the most used pistol is the Glock 34.
That puts you in the SSP division. It think if you mess with it enough it can put you in ESP divison
I know this is old from 2007 but it says a lot about what people are running
I compete in the SSP division with my Glock 34 gen 4. I pulled out all the internals and polished everything to a have a 2.75lb trigger pull. I changed the sights to Warren tactical sights. Blade tech holster and magazine holders... I left the barrel and the recoil spring alone.
I started with a stock G19, but didnt start winning anything until I started to practice and upgrade to the G34 with the homemade trigger job. Then things started to come together.
I also handload my rounds for accuracy and meeting power factor.
I will flying out and competing in the 2012 IDPA national championship this September.