Charlie Ticket (flimsy little thing you stick into the machine to read the magnetic stripe) price is $2 for entrance to the subways.
Charlie Card (like a credit or hotel card) is $1.70 for entrance to the subway.

CharlieCard therefore saves you money. No reason to use a Charlie Ticket over Charlie Card. The only thing is, the automatic kiosks only dispense CharlieTickets. CharlieCards can only be gotten at select kiosks or through asking MBTA employees, as most locals already have them. CharlieTickets are thrown away after all the money is used up on them (well, you could refill them...) whereas CharlieCards are just refilled when you need more money on them.