Dielectric constant is a property of material, hence it should be same unless there is an impurity or crystalline structures are not identical

Mono layer, defect free, free-standing graphene will show higher deielctric constant.. and chances of synthesizing this by Hummer's method is remote.. so CVD graphene will show higher dielectric constant.

CVD method is used to prepare the higher deielcrtic constant graphene，while Hummers methods is always used to prepare GO，then GO was reduced to RGO. RGO is not real graphene, it is an grahene derivative.

There will be.  CVD gives good quality graphene where as graphene produced using Hammers method (rGO) may have some remenant functional groups with it,  thus leading to different Dielectric constant.