G3 Valk and G3 GP doesn't exist.
The only people buy the G36E valk is because of the perm option. The differences are barely noticeable, even the spread.
Recoil/ Spread/ Texture. Thats about it. Rest depends on skill.
@Shadowxeno-Backup
CoD4 has G3, but it's full name is H&K G3A4 or H&K G3A4A1, not H&K G36 nor any of the variants.
Google them, they are different series.
@Bear Jew
Please explain the difference between the G3 series and the G36 series.