They are not quite equivalent – at least not in the general case. The code using an object initializer is closer to this:
Position tmp = new Position();
tmp.x = 3;
tmp.y = 4;
Position position1 = tmp;
In other words, the assignment to the variable only occurs after the properties have been set. Now in the case where you’re declaring a new local variable, that doesn’t actually matter, and the compiler may well optimize to your first form. But logically, it does matter. Consider:
Position p1 = new Position { x = 10, y = 20 };
p1 = new Position { x = p1.y, y = p1.x };
If that did the assignment to p1 first, you’d end up with 0 for both p1.x and p1.y. Whereas that’s actually equivalent to:
Position tmp = new Position();
tmp.x = 10;
tmp.y = 20;
Position p1 = tmp;
tmp = new Position();
tmp.x = p1.y; // 20
tmp.y = p1.x; // 10
p1 = tmp;
EDIT: I’ve just realised that you’re using a struct rather than a class. That may make some subtle differences… but you almost certainly shouldn’t be using a mutable struct to start with 🙂