В каких случаях лучше использовать класс с параметрами?

public class Pair<TFirst,TSecond>{
    public TFirst First;
    public TSecond Second;
}

Pair<int,string> pair = new Pair<int,string> { First = 1, Second = "two" };
int i = pair.First;   
string s = pair.Second;

public class Pair{
    public First,Second;
    public Pair(int x,string y){
       First=x;
       Second=y;
    }
}
Pair pair = new Pair(1,"two");
int i = pair.First;   
string s = pair.Second;

List<double> list = new List<double>();

List<int,string> pair = new List<int,string> { 1, "two" };

Pair<int,string,float, *и т.д.*> pair = new Pair<int,string,float, *и т.д.*> { First = 1, Second = "two",Third=4.56, *и т.д.*};

class Pair<TFirst, TSecond, TThird>
{
   public TFirst First { get; set; }
   public TSecond Second { get; set; }
   public TThird Third { get; set; }
}