Bonus Coupons Vs Print Credits

Can somebody clarify the differences between bonus coupons and print credits. 

From my understanding they both are tied to items (collections) and not a $ amount. 

Are the main differences that you must add a print credit to an existing account (bonus coupons can be "free floating") and that you can also have a partial cost associated (whereas print credits are just "free" items in whole)?

Print credits is basically a collection for free. 

Bonus coupons are basically a collection but can be free or a set price, can require a minimum cart amount, etc...

Read about bonus coupon here.

Thanks Tim, yes I read all the manual writeups about both of these before posting, but the specific info you just posted here is helpful as well.