While the mainline is 4.e5!? Ng8 5.Nf3 Nc6 6.c4 cxd4 7.Nxd4 Nxe5 8.Ndb5 a6 9.Nd6+ Bxd6 10.Qxd6, I see quite a few players are choosing 4.Nf3!? Nc6 Be2.

How to decide which to play in a particular game?

At first I thought 4.e5!? for the win (as in Bacrot-Dorfman, Marseille 2001)  in most cases and 4.Nf3 when I only need a draw (as in Tal-Dorfman, Marseille 1989). But Black has options line 4...b6 which don't lead to a quick draw. So now I'm thinking it's best to simply focus deeper on c5 and only use Nf3 as an occasional surprise. Thoughts?