You know what's weird? I asked Para about that...my early LDAs have smooth triggers, while my new one is serrated. Their customer service guys told me that the serrated triggers were added because of "overwhelming" customer demand. They thought it was weird, too, since all of us have spent years grinding the serrations off revolver triggers.
Luckily, my Carry 9 is Old Skol with a smooth trigger. BTW, in ev ery class I've gone through I end up with a shredded trigger finger regardless of gun...I apparently have girly man hands...
Michael B