@Andrei:I think simple man never distinguish G1 from G2 or G3.
I understand what you mean ;) but is not always correct

G2 means to have a continuity of the curvature when join two curved surfaces together
It's obvious that is useless if your surfaces are flat,like Danny correctely says
But it can be useful for you because it give you a real smooth junction and speed up your workflow
I know that your target is rendering so: is it better to have a clean surface made from a G2 blend,quickly?
I suggest you to consider this option when you model and when possible,it will give you better results :)

Consider this like a kind suggestion without misunderstandings..you got this option..use it ! :)