Depends on your purpose. For transport to a range or something, any of that foam will work. If for some reason it will be long term in there, better not get the type of foam rubber that is open cell, that is, the little bubbles are open and act like a sponge. It will not take long to wick off the oily film on the outside of the gun, where it is in contact with that foam rubber it will be bone dry in a short time. And if any moisture contacts the foam or the air is maybe very humid or there are wide temperature changes with moist air, it will act like a sponge for moisture too. Some foam rubber deteriorates over time and gets crumbly too, but that is usually over some years of time. But I suppose in a dry place like a climate controlled home in a closet, the risk is not as great as say, a garage or basement. That thing of expanding foam spray with a plastic lining is not so bad, I have seen that used to fill transport containers for delicate instruments. But it is denser and heavier than foam rubber so if the case is a lot larger than the gun, it is a bit heavier. I sort of like the Glock tupperware containers for handguns. Notice how they have a peg to go thru the trigger guard and secure the gun from rattling around, and there is only plastic in contact with the gun, no foam or scratchy materials. And they seal like tupperware. Someone could make those style gun containers for other guns and sell them well.