a single trigger just shoots as you pull, the 2 stage has a take up until you feel the "second stage", then it is the final pull. The single stage is good for hunting and is an American standard, The two stage is a more military and European thing and can be seen as safer. It is easy to get used to either style.
Mmmm, the two stage is so smooth! I don't mind either of them, my ar has a Rock river 2 stage in it and I am quite fond of it. It helps me be a little more precise.
In my opinion, the two stage trigger is the "normal" trigger.
It is the trigger used on the 1911 and a whole line of Military rifles since 1860 or so.
The single stage trigger, by its design, has creep in it and can be hard to discern when it will release the hammer. The two stage trigger does not have that ambiguity. It is very easy to make the rifle fire precisely when you want it to.