GM and heres why...
1) easier to maintain and should last longer than white after the years
2) easier to color match if you are gonna have kits/cf pieces
3) less common comparing to pearl white Z
4) head turner with or without the sun (especially the flat GM color when the sun is not out)
At the end, it all comes down to personal tastes and prefrences. And i have to respectfully disagree with the "grass is always greener" on the other side comment. Cause we all know that if we will choose a black Z if we have to all over again
