The Spartan II's do outmatch the IV's, and yes it is true that with armour on, the IV's are pretty on par with the II's in terms of strength and speed (I'd say the II's get a slight advantage due to their more rigorous augmentations) but these points are not what truly separates them. Spartan IV's are adults, mostly with military backgrounds, volunteers to be made Spartans. Men and women with memories of a life once lived, feeling and emotions of family, friends, lovers and still have these same feelings after augmentation. Spartan II's were abducted at 6 years of age, hand picked due to genetics. Indoctrinated before even becoming old enough to discover who they really are, developing their own personality. Their entire lives going through rigorous military training to be the best of the best, to win against all odds and to be fearless. The Spartan II's are the personification of war. War is all they have and will ever know. That's what truly separates them from the IV's.
Who is Stronger Spartan II Or Spartan IV