They have slight differences.
5ply vs 3 ply engineered wood flooring.
Multi ply engineered wood flooring is made up with 3 6mm hardwood veneer quality plywood structure.
It is a stronger flooring option will last longer is more resilient and resistant to warping and is overall more durable than 3 ply.
It s not very moisture stable because of the thick sliced wood it is made of.
As far as 3 ply to 5 ply all i can tell you is i have installed both and they were easy to work with and fit well.
And it s not all hardwood in most cases softwood cores are the norm now.
When deciding between 3 ply and multi ply engineered wood flooring remember to think about the conditions in the interior where the floor is to be fitted including the moisture content of the sub floor.
A multi ply board is less likely to risk damage due to moisture and temperature fluctuations as compared to a 3 ply board.
Ultimately we believe multi ply engineered flooring is the best option.
It looks like all that material has been discontinued.
It has the same wear layer a a reall hardwood solid floor.
The plywood is normally cross structure with 1 5mm thick of each ply in odd number 5 layer 7 layer or 9 layers and with the back layer same grain direction to the hardwood veneer lamellas.
I looked in my area for the old 5 ply laminated wood and could find none readily.
Structurally i believe they are both the same.
Whether or not you have under floor heating.