I've hired someone to come and install some better modules on our level 4 base. (atm I'm limited to an upkeep of around 200 mil)

I'm just wondering what's the best ratio of armor to attack/defense.

Would it be better to put in something like 61k hull/ 11250 defense or 76k hull/ 9650 defense? or something else?

personally i would go with the higher hull.
and the best defense for level 4s is the fact that they are level 4, people will either go for easy badges (level 3s) or they want the base large/massive/colossal base crates