The 2 stage trigger allows you to load the trigger and get to the wall of the 2nd stage without any concern of breaking the shot. Many shooters like this feature as you can get your finger on the trigger as you settle into your reticle placement and prepare to break the shot. The weight of the 1st stage gives you the tactile feedback that you in the "safe" 1st stage. Typically, 2 stage triggers have a higher total trigger pull weight, but the perceived weight of the 2nd stage doesn't feel as heavy because you are already holding the weight of the 1st stage.
You can absolutely do the same thing with a single stage trigger, it just requires the discipline to place the finger on the trigger without putting much if any weight on it. This is especially important if you have a single stage trigger with a light trigger pull weight.
Watch other shooters (particularly with light trigger pull weights), I bet you'll see at least one who does a "touch and go" on the trigger several times as they settle in to their final pre-shot position. In a PRS style event, that is wasted time and I would bet they'd get on target faster and break a shot with a 2 stage trigger if they are so tentative with a single stage.
It's a personal preference, the bullet doesn't know the difference.