well depends tho , both interior design is different

thats depends on you as you are the one who is getting the car , test drive both of them and make a comparison , and heck , choose for yourself , we only can comment bout overall , final desicision is still on yourself , so 350z and gt you decide it

and since your dad is getting it -.- why not choose both LOL well you have slk at home , why not add in another gt or z ? instead of choosing either