I use VGL loaded with infernos a lot. I dont play with smoke in balanced games, as its too easy to abuse, but the VGL with infernos or frag are very useful.
With Frag, its a preemptive APOD. So while the Apod has the advantage of being reactive, triggering when infantry get close, the lower tech VGL has to be triggered manually.
The real value of VGL is that it is a source of AE damage. So when dropped as a bomb into 1 hex, or fired into the 3 hex arc, you deal 2d6 burst damage against infantry, and then double it for being an AE weapon. So while you cant stop infantry in the same hex or before they ambush you like with an apod, you deal lots of damage, to potentially lots of infantry, with the VGL.
Versus battle armor, the inferno attack is an AE attack, so it hits all troops. So 2 VGL on the shadowhawk, loaded with infernos, versus clan elementals will deliver 10 inferno hits to a squad of 5, killing 3 of them. Versus conventional infantry, the inferno attack is worse then frag, as infernos only remove 3 troopers for 1 missile hit; I dont think AE helps with how infernos and infantry interact.
With all the stealth battle armor hopping around and being impossible to hit, a collection of inferno VGLs are one of the few non-artillery ways to hit the buggers, and they dont explode at 10 heat like normal inferno SRMs do.