Ship here is:

RGP + Stealth Device + PtL + Autothrusters

Enemy ship is a naked Chewbacca, shooting with turret through front arc at range 2.

Which gives a better average # of evades?

1) Actions: Barrel Roll, then Boost, taking RGP outside of Chewbacca's front arc and getting Autothrusters' ability OR

2) Actions: Evade + Focus, does not get Autothrusters' ability

Assume that either way, RGP still winds up at range 2 of Chewbacca.

For purposes of this question, ignore cost-efficiency. So, "1 is better because otherwise, you would have spent points on Autothrusters for nothing" doesn't matter.

That should be obvious.

If you're talking about taking an evade action in place of setting up for autothrusters, the end result is exactly the same, if you roll a blank on defense.

If you don't roll a blank (e.g. all evades/focuses), autothrusters doesn't trigger, therefore evade token is better, so with that information alone you have your answer.

Add on a focus token and it's icing on the cake to why F+E is a better choice than doing neither in order to trigger autothrusters.

If it were more than one attack you were defending against, the answer may change.