How much power do you need? If max torque is your goal the ASTRO Thor and the Aircat 1250K pretty much define that category. If you need something with more than enough zip to do tires but is quite small the ASTRO Nano is hard to beat. It was great for tearing down a Powerstoke 6.0 that I recently rebuilt.
I have the 1250k and even though it's pretty powerful, I think the real calling card of this tool is *smoothness*. It's so smooth you really tend to underestimate how powerful it is. It's not very loud and the lack of vibration almost gives you cognitive dissonance because your senses are telling you it's not really doing work because its so smooth.
But I assure you it is doing work. The reason it's so smooth is that it's a pin clutch impact mechanism instead of a twin hammer. The mechanism rides in an oil bath and has no grease.
As much as I love my 1250K I don't use it all that much. Why? Well, you simply just don't need that much tool very often at all. The thirst for more power is causing us to lose sight of the fact that the more powerful the gun is, the less likely it is that you'll need that power over a smaller more compact gun. At some point, that last increment of power is a poor tradeoff for size, weight, noise, air consumption, etc.
Which means that the air gun I use the most is
my HF version of the Capri/Hazett gun. It's notably lighter and less bulky than the 1250k and works just fine for even rusty bolts under 9/16"-to-M14 range. It's nothing at all close to 1000lb-ft like the HF claim is, but it does have a good power to weight ratio, is well-made, smooth and not too loud.
The truth is, making an air gun more powerful is easy. But it's not about just power, it's about how
useful that power is in terms of where it fits and how fatiguing it is to use (weight, noise, vibration).
Something like an Aircat 1375XL at 2.75# is probably worth considering if you realize you don't need brute power often. It's a pound lighter than even the HF gun and you will absolutely notice the lighter weight.
If you value your time that highly sell all your tools and pay a mechanic/carpenter/electrician/ etc. etc.
I think they have improved in recent years.
