difference between Function and new Function

The spec (page 127) says they're identical.

15.3.1.1 Function (p1, p2, … , pn, body)

When the Function function is called with some arguments p1, p2, … , pn, body (where n might be 0, that is, there are no “p” arguments, and where body might also not be provided), the following steps are taken:

1. Create and return a new Function object as if the standard built-in constructor Function was used in a new expression with the same arguments (15.3.2.1).

---

However, you should avoid the Function constructor at all costs.
It needs to eval the string you pass to it; eval is evil, and slow too.