You can't really approach the decision in that manner. It's
not a matter of one being a "better bird" over the other.
They are all different, even within the same species. All
you can do is indepth research of both and try to decide
which might best fit your life style. But if this is your
first bird, you need to start out with researching what is
involved in living with a bird of any kind. It's not a cheap
endeavor, it's time consuming and labor intensive. Review
the amount of time you have to spend with one, how expensive
everything is, especially how expensive Avian vet bills can
be, assuming you even have one near you. Lot's of folks
don't have one within reach. And for sure, review all the
dangers in your home that you will have to get rid of and
stop using before a bird comes home. If you haven't already,
check out this information.
Generally speaking, neither of those two are recommended as
first birds, for the novice owner. The Greys especially can
be very complex.