Static Mesh as Terrain

So recently i’ve discovered this video : Sunrise - realtime environment rendered in Unreal 4 - YouTube

And I was inspired by it to see if an open world scene could be created with a similar terrain look.
Now after making the terrain in world machine I tried out a few alternatives. First one was to import it at a 1k resolution in unreal directly and enable smooth shading through terrain materials.
The second one , I exported it as a high poly mesh and imported it to ZBrush and decimated it and exported it again.
Importing that mesh into unreal afterwards.
Now the second option looks much better and much closer to the video but the disatvantage is that it’s a mesh.
The terrain is around 4x4 KM in size.
Now my question is , would it be worth continuing with a mesh instead of a terrain? Does it have any advantages? Because I am thinking about texturing it and it will prove to be difficult to have detailed textures for that size.
Would I need to split it up into chunks and texture each individually? Would it be better just to roll with the unreal terrain , for it’s many advantages?

Any tips would be appreciated!

Unreal terrains are massively more efficient than a mesh of the same size / polycount. I can’t think of any upsides to going with a mesh - though if you’re saying that you can’t get the result you are after with a landscape, but can with a mesh, that WOULD be a good reason.

A 1k height map for a 4km terrain is one sample every 3.9m, which isn’t very detailed. How dense is the mesh you exported to Zbrush?

The terrain system in UE4 has optimization features, so it will adjust the geometry level of the terrain based on where you are, plus there’s stuff like terrain materials and foliage that’s all designed for it.