Hence the acronym MAPP. Acetylene tanks have acetone in them, which absorbs the acetylene gas when under pressure, and easily releases it when depressurized. The acetone is also soaked into a fibrous material inside the tank, further stabilizing the mixture. Acetylene gas by itself is very unstable and can't be stored safely. MAPP can, and is much hotter than propane.
The little outfits with the disposable cylinders are intended for hobbyists with small and/or infrequent jobs. If you rarely use the torch it takes quite a few of those $7.50 bottles to equal the cost of a filled oxygen cylinder ($90-$100 for the cylinder, $10-15 to refill, so let's go for the high of $115 -- $115/$7.50 = 15.33 small cylinders). The 20 cubic foot oxygen cylinders have to be tested or replaced every 10 years too, so there's a "shelf life". Every 10 years you have to swap it for a tested one at 1/2-2/3 the price of a new one. There's an equal shelf life/cost for the acetylene tank. Those $250-$300 outfits with "pony" tanks aren't filled, so add another $40-$50 to have them filled.
Is there an adapter so that the torch outfit can be used with a regular small oxygen cylinder? That might be the best of both worlds. Then you could use the MAPP gas (or even propane) with a regular oxygen bottle, since the oxy bottles are the biggest expense. I'm pretty sure there is (or used to be) an adapter. You don't normally see propane used with oxygen, but add oxygen to ANY flame and it will get hotter!