By pressure tank, I presume you mean a CO2 bottle. Those are really nice in the gas is actually a liquid. So as it boils off inside the bottle you get huge amounts of gas volume in a small container. I ran one for years. It can fill a LOT of tires. They do have to be mounted upright to avoid getting liquid into the regulator. They do need refilling. You can't judge how full they are from the pressure. Pressure is dependent on temperature, unless you are out, then there is no pressure. The only real way to know what you have is by weighing it. So remove it, know the weight of it full/empty and see how it compares. Then there is getting it filled. Exchange is often possible, but you will likely get a heavy steel bottle back in place of your nice aluminum one. Keeping your aluminum, every 5 years it needs a new hydrostatic test to keep it current. And some people get all fussy about a bottle of compressed gas inside a vehicle. While CO2 isn't CO, it also doesn't have and free O2 to breath either. Fill the inside of a vehicle with CO2 and it isn't a habitable space. Isn't toxic (CO is very toxic), not going to poison you, you just don't have oxygen to stay alive. Causes hyperventalation and a feeling of panic.
Some will run N2 (pure nitrogen) as a compressed gas. Not as much volume as CO2, stays as a gas, but at a higher pressure. This you can know how much is left by checking bottle pressure. Can be used in any position. Still has the 5 year hydro requirement (as do all of the high pressure tanks). Not may people use this. Seen more in the race world as it also is used for charging shocks.
Last of the pressure tanks, scuba tanks. Very much like Nitrogen, but it is just air. Filled at most any scuba shop, maybe a friendly fire station if you know them fairly well. I've run this before I got my CO2, and after I sold it. Also handy for diving, which is why I have some around. With the growth of paintball guns that run on compressed air this stuff is even more available today than ever before.
There is also the ~5 gallon tank that is filled with shop air. This is relatively low pressure, 100-150 PSI. These are even bigger and don't have the volume to air up large tires. I don't even consider these for the trail due to the lack of volume and the shear size of them. They are good when you have a flat tire in the parking lot in a car and you can use your nice home/shop compressor to fill this tank and take it with you.
Compressors are nearly limitless, but have limits. You will have little ones. Between taking forever to fill a large tire, they often have heating issues. Most can run long duty cycles. Good ones will reach a thermal limit and shut down and will start again once cooled off. I've had some that I placed against the dash so the A/C vent would blow on them to cool them off. I have even done this with a small 12V compressor running on an invertor.
Now the big compressors. Several people at work have recently stepped up to these. Typically the ARB twin air or the one that looks exactly the same minus the ARB naming. They do suck down the electrons. I recently added one of these to my collection. It can pull a solid 70A on the top end. That is pretty much one HP of electricity. And you do get a lot of air for that. Straight off the compressor I was pretty impressed with what it was putting out into an air nozzle. Doing tires like nobody's business. Spun the impact pretty good. But I ended up putting a small air tank into the mix. The impact flows more air than the compressor can keep up with at pressure, so that buffer works and the compressor doesn't short cycle as bad.
The CO2 and scuba tanks do work. But knowing how full they are, getting them filled, can't really install them deep as they have to come out often. The compressor I am liking better. Installed in an out of the way location. Small air tank that doesn't have to come out to be filled, also tucked away. Limitless amounts of air. There is compressor run time, and depending on how you are filling the tires the compressor is potentially slower. But it is always there.
Lockers make for more issues. If the lockers never leaked anywhere it wouldn't really matter. But so many lockers have small air leaks. Small leaks and time are not the best mix. Having to turn the gas bottle on to use the locker. Leave it on all day, and how much was lost in the leaks? The compressor will always be there.
The last truck I sold had an air horn (and air kickdown for the transmission). Ran off a compressor (a really tiny one for factory air suspension). Always ready to go. Any time I drove it the air horn was ready, the small air tank was charged and ready to go. Leaked out after sitting for a bit, but filled right back up when I turned the key on. But that would never work for filling a tire.
