Two stage triggers tend to be more expensive. Many high end rifles have them because a shooter can pull back until right before the break point to get the final alignment and sight picture before firing. Single stage triggers can be set to a really low pull weight, but with gloves or high energy adrenalin pumping through your body, many people consider a very light weight trigger unsuited for tactical or hunting use. Many tactical rifles have a single stage tuned remmy or timney trigger set to ~ 2.5#.
Straight triggers are seen more often on bench rest or varmint rifles. I don't care for them because I like a trigger shoe that contours to my finger tip.
Although I enjoyed shooting a friend's custom bolt gun with a huber two stage, my rifles all have single stage triggers. I have an old school Remmy on my Rem 721 hunting rifle, my wife uses a 1.5# timney on her rifle, and I have a 2-2.5# jewell on my my Surgeon. I have also had rifles with tuned x-mark. I prefer the jewell but I concede that other triggers may be better suited for a rifle that will see very hard use in harsh environments.
If I was building a rifle from the ground up, I would probably get a two stage trigger just to try something different. If I didn't like it, I could always trade it for a tuned remmy or timney and a little bit of cash.
Hope this answers your questions.