Coming from my "answer" to question "Stopwatch in a Task seems to be additive across all tasks, want to measure just task interval"

What are the possible differences between creating a new Stopwatch instance as:

Stopwatch timer = System.Diagnostics.Stopwatch.StartNew();

with 

Stopwatch timer = new Stopwatch();
timer.Start();

Implied subquestion:
Why was StartNew() method provided?

c# .net system.diagnostics stopwatch
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