I recently got a Grizzly drill press and am wondering whether it's
worth upgrading the chuck.

What advantages would a Jacobs chuck give me? They are rather
costly. Are they worth the price? Heavy duty or medium duty?

My machine came with a 0-5/8" chuck. It appears that if I want such a
chuck I have the choice of a 0-1/2" or a 1/8"-5/8" but there is no
0-5/8". Now I'd rather not lose the low end and I have no clue what
things anyone sells that have a shaft over 1/2". What would I be
missing out on if I put in a 1/2" chuck? (I could, of course, keep
the existing chuck in reserve.)