Construction decides where the floor can go, how often it can be sanded, and how it behaves over underfloor heating.
A solid plank floor is one continuous piece of timber, typically 20 mm. It can be sanded many times and lasts for generations, but it moves more with the humidity of the room and needs space to do so.
An engineered floor has a hardwood wear layer over a cross-bonded core. The layers run at right angles, which makes the floor considerably more stable — usually the right choice over underfloor heating and on concrete.
Tell us about the subfloor, the heating and the room, and we point at the construction first and the look second. That order produces the fewest disappointments.