In my latest playthrough I play a VATS-oriented character and I can say this:
VATS really shines when you are in a close range situation where you're overwhelmed with enemies. It switches targets seamlessly and usually maintains a 95% hitrate. You also get a 6% bonus to crit chance. At medium to long range, manual aim tends to be more effective for me, though.
In terms of weapons, certain guns work better than others. Some uniques are cheaper to use in VATS than their counter parts. Lucky for example is about 33% cheaper in VATS than the regular .357 Magnum Revolver, whilst also having a bigger crit multiplier (making that 6% crit bonus really count for something). Take the right perks and this seemingly light pistol turns into a almost-all-crits beast in VATS.
Shotguns on the other hand are unreliable, though very strong. The high AP cost makes missing more costly, and they seem to miss more despite 95% accuracy. In my experience, using slugs or ammo that reduces spread seems to boost the effectiveness of shotguns in VATS, but I still prefer single shot weapons.
It's very easy to get too many VATS perks and end up with more AP than you'll ever spend. In my latest build I went for:
- AG10 (Implant + 1x Intense Training)
- Fast Shot (really accentuates short range effectiveness)
- Gunslinger
- Action Boy (x2)
- Grim Reaper's Sprint
When I coupled these perks with a low-AP weapon like Lucky and occasionally used Jet, I found I never ran out of AP to spend. In fact, I coud've probably cut one rank of Action Boy.
This build makes those hard gunfights where you get overwhelmed a lot easier to manage, but most of all, makes them extremely gratifying.
To take an example, I helped Cass take revenge on the Crimson Caravan and the Van Graffs. The Van Graffs are pretty tough, but one round of VATS easily wiped out 5-6 Van Graff Guards, with me taking neglible damage (don't even get me started on those Crimson Caravan pansies). Crits start flying, everything's dead before the first revolver case hits the ground. It feels like playing in a spaghetti western. Really enjoyable!