Let's take them in order:
IGLA - will prevent the truck from being started, will prevent key programming/deletion
Tazer - KINDA purports to do some of what IGLA does, but very buggy and problematic - has been known to damage electronics.
Compustar w/ drone - makes noise when triggered, has a basic starter-inhibit mechanism, provides GPS tracking
Ravelco - Fancy kill switch - easily bypassed.
If you were to get just one, I'd vote for IGLA. It's the only one to virtually guarantee the only way they're taking the truck is with a flatbed. The only issue w/ IGLA alone is there's no deterrence - nothing to "scare" the thief away. Compustar adds this deterrence factor w/ an alarm siren, shock/glass break sensors, and when coupled w/ Drone, will let you track the vehicle, even it is loaded on a flatbed.
Tazer is a half-assed attempt at security, done as an afterthought to a product that was originally designed to modify a few creature-comfort features in the BCM, and do stupid flashing light shows ("Ooh, look at me - all my lights are blinking").
Ravelco is a kill switch, nothing more. It offers a modicum of protection against the uneducated thief, who just knows to plug in his laptop/tablet to "dis connekter here" and "click on dat". Against a determined and educated thief, it's a minor annoyance, and not much else.
One other product I'll throw in the mix, in the deterrence category, is the add-a-shock sensor, which is a simple add-on product that trips the factory alarm when any type of shock/impact is detected. Coupled with a horn relocation, it's a lower-cost alternative to Compustar, but (obviously) without the GPS tracking.
For the best security, covering the widest range of scenarios, IGLA + Compustar w/ Drone gives you the best protection, short of a 24x7 armed guard. For THAT level, look into TrunkMonkey<tm>