Infantry vs vehicle turrets ought to have massive bonuses to Stealth if you want to reflect the typical tank vs infantry cat and mouse game. Typically the cinematic idea behind this is that the limited view offered by a turret doesn't give you the full situational awareness being outside would.
EG, if there's dense terrain, infantry should win and be able to get close and either enter the vehicle or target a weakspot, whereas in an open plain tanks are king.
I would give Vigilance checks by the turret -2 setbacks, while stealth checks would gain +2 bonus. That way anyone bothering to be stealthy would probably live, whereas anyone who felt like they could hop around in the open gets shot.
Note that this DOES make gunners with High Vigilance and equipped with the appropriate scanner equipment extremely lethal.
The best strategy for the PCs is to use this stealth bonus to approach until they're engaged with the gunners, and then go Captain America on them, as you typically see in action movies.
Edited by TarlSS, 07 April 2014 - 08:49 AM.