Well I dont have the guns your talking about, but I do have a similar collection (ca g36c and a gg m4a1) honestly, you cant go wrong either way. I cannot comment about the star g36 dont have one never even touched one, but I can say that the GG is a great gun, fairly well built and has decent accuracy. Although if your using it for CQB it might shoot a bit too hot, mine is in the 370ish range. Also you will eventually be dropping a pretty penny on the M4 for a metal lower when the clear plastic one kinks out.
Theres way more to this than I can imput, but hopefully this gives you some perspective