I'd take
Gregory over
Cosmo but I am not really fond of either.
Gregory is a nice name, nothing wrong with it really. But I grew up with enough Gregory/Greg/Greggs for it to just seem a bit tired right now for me. 100 year cycler.
Cosmo just seems a bit silly to me. A perfect name for Kramer, a fairy godfather, or a pet...but not a really life person.