I would suppose it makes a difference what you mean by "difference". In my mind, and on my '82 Custom, it really seems not to make as much a difference in handling as the right fork oil does, but both apply the dampening needed to get things right. It seems to be one of the harder balancing acts for the normal front ends on these bikes. That may be why so many seek out other front end arrangements to suit their style of riding.
10 to 16 pounds of air pressure to assist the spring rates, and the oil, affects a perfect set up. You can't rely on the air alone to make a whole lot of difference, since the fork seals are the "keeper" of the keys. Everything must be just right, and each rider will have a space they are happier with.
My experience with my air assist has been that the pressure is difficult to judge precisely, since most air gauges are somewhat inaccurate, within the degrees of error to make it curious. Best bet is to go on feel in that case, but never use any compressor type supply!!! Hand pump only!
And, again, everything regarding the air has to be based on the integrity of the seals.
The logic behind air forks is that they're so tunable at the user level. You can start with a soft spring for the plush ride, then add air when you want to stiffen it up to adjust for weight or firmer handling. As the fork compresses, the air pressure increases and the effective spring rate changes, so you don't pound down into the bump stops with the soft spring. The amount of fork oil is also a factor in the tuning, since raising and lowering the level changes the amount of air, which will change the spring rate at the same point in the fork travel. A high oil level will make it stiffer quicker.