Honestly it depends on whether they are getting their degree or not. Each are finishing their 4th year so they may be graduating. If they have no interest in grad school its a choice of playing in college or getting paid probably more money than 90% of their classmates will make their first year out of college. I don't think either one of them improves their "draft stock" by coming back. Gbinije is a possible 2nd round pick likely NBDL/Europe player and Cooney can make money overseas. Another year of college won't change that for either of them.
Personally I'd love to see them both go for a graduate degree...just because I'm a Cuse fan.
I think G could play himself into being a first round pick if he has another good year next year.
I know Cooney is never playing in the nba, but why give up a year of playing big time college bball for something that will always be there?