The advantage of low pressure is that it is 'easier' on the inline regulator. All regulators won't blow up or anything it if is fed high pressure air, it supposidly is just easier on the regulators. The disadvantage is that not every gun can use LP tanks (Angel LED, LCD's to name one).
The advantage to high pressure is that, well there is nothing bad about them, but there is nothing good about them. They serve their purpose well. The disadvantage to them is not every gun can use HP air(Angel Speed to name one).
I think if I were to buy a single tank and use that only, I would probably get a Crossfire 68/4500 LP tank. However, if you were going to get a HP tank there is absolutely nothing wrong with HP tanks. People have been using them for years without any problems, so don't think if you buy a HP tank something bad will happen to your gun.
I enjoy adjustable tanks...instead of sitting at a low pressure or high pressure setting I can put it at say 500 psi and run my gun at just over the needed pressure. Most guns will preffer a hp tank even to the point of the tank might not keep up with the needed air flow. Very few tanks REQUIRE a lp tank but it is true that the angel speed is a pain in the butt with a hp tank ofter not going down low enough for the needed fps.
There is no performance advantage to LP, except that it may be slightly gentler on brittle paint.
The DISadvantage is it can be less effecient, and can starve your reg.
But ultimetly, there is no difference. Every paintball gun is tuned to a specific PSI range. Most blowbacks are tuned high, and most spoolers are tuned low.
The rest (ramvalves, and cockers) are usually in the middle.
The LP myth started with Smart Parts. The original Shocker used cheap solenoids, and could NOT run HP. It could only run LP. So, they invented a story where it make the gun more accurate.
They even put it in the patent!!
BUT... NO TEST HAS EVER shown any performance difference.
Its LP and HP is just part of fine tuning your gun to a specific range by adjusting springs, hammers, dwells, etc.
Its just like how you can get a bigger CARB for your engine, but if its too big, then you loose power and effeciency. Everything is a balance.
Okay most tanks that are low pressure are around 450PSI. This by no means is super low pressure, but it is lower than say 850PSI. I have a low pressure tank on my DM4 and at the high rates of fire I shoot it at, I never get shoot down with it. I think if my LP supplies enough air to my DM4 at high rates of fire, it should be capable of supplying air to other markers at high rates of fire.