More expensive to buy and more expensive to operate.  A skid steer size mulching head is probably going to cost between 28 and 35 thousand and will require high flow (45 gpm) to operate.  Personally, I prefer a disc head for what you want to do; the price is about the same.  Expect to pay somewhere around 125 to 150/hour for a mulching head; a mower would be less.