Just try it, it depends on your fighting style. Vulture is fast and really good at sticking on a target, so i prefer as much firepower over a long time, as i can get. Both, burst & beam (class3) eat way too much power to be effective - you have your target locked in front of you and wait for energy.. and wait, and wait... But if you prefer burst dmg, you can go with really expensive beam laser for like 2,4mio each. Shooting time is about 5 seconds straight with 4 pips into weapons, but the effect is really nice - shields just melt rightaway. But then the strugle for hull damage and power begins ^_^
Pulse E3/G gives me about 25sec of firepower before the capacitor is empty. And i can still shoot with 4 in shields and 2 in weapons, thats a great advantage against multiple targets (because your shields can take a hell of a beating and mainly because vulture has exposed internals - without shields even the easiest npc can do heavy damage to modules).
Note: this is for PVE, RES farming. PVP will be completly different, there i would think about a heavy beam laser + cannon/rail/plasma.