Generally a lighter trigger will give a good shooter more forgiveness in small trigger press errors. However, it usually won't t mask serious shortcomings in a shooter's fundamentals. A shooter that puts rounds low/left with a stock glock is still going to put them low left with a 3# glock trigger.
I find the consistency I can hit extremely fast splits goes up with a light trigger (I.e. In the .11-.13 range), but so does my propensity to trigger freeze, so none of my competition guns have anything more than a minus connector and a 5# striker spring, and some polishing.