I think the first thing to say about the Counters in HOI IV is that they are not the actual individual units but an overview of all the units in a province at a particular moment in time so a Counter in HOI IV can be 1 Division or 10 Divisions it is not a single unit though it can be at certain times.
I would suggest that its better to conceptualise a Counter in HOI IV as a means of communicating information to a player that just happens to look like a Counter, its telling you how many Divisions and what type are in a province their overall strength and organisation and what country they belong to but its not comparable to a Counter in HOI III, the Counter in HOI III is in fact comparable to the Sprite in HOI IV.
So the first Question you should ask is a Counter in HOI III superior to a Sprite in HOI IV with regards the information that it conveys to the player and the answer is clearly yes.
Next question you should ask is a combination of the Sprite and the Counter in HOI IV with regards the information that it conveys to the player superior to the Counter in HOI III?
I would answer yes and no, the Sprite is almost irrelevant at most zoom levels and while the Counter itself is giving you an overview that you did not have in HOI III most of its information is exactly the same as the HOI III Counter, Flag, Division type the only real difference is that at a glance you can tell how many and what type of units you have in a province.
The final Question you should ask would a combination of a HOI III Counter and a HOI IV Counter be superior to all of the above and the answer is unequivocally yes.
And why do we not have that ? Because Paradox wanted a 3D world with 3D models.