Just to put in my 10 pence worth.
If you just want an MCC certificate do it as cheap as possible. However if you intend to go down the airline assesment route spend your money on a decent course with a sim that puts you at ease when you are confronted with a 737/757 type for your assesment. The airlines dont mind you having practised on a decent simulator as they would expect an enhanced performance., however it makes you feel more confident so that the whole thing is not such a big surprise.
I speak as a 20000+ plot who is now an MCC instructor.