#1-you overspend because you worry about it later. thinking you will just return it. (reality: it ends up being too much effort)
#2-the money accumulates and end of the month, what?!??! $7689!
Best to use:
Cash-pay now.
Why it's the best? The fact that you reach for the bills and count them one by one will make you realize mentally how much you're giving out for the purchase. Oops, $20 gone. another $20 gone. $10 gone. two $5 gone. How many bills are left?