Modelling game terrain

Unity's terrain support is based on height maps, which can be painted inside the Unity editor itself or imported from bitmaps. It can yield impressive results (eg. check out TTT: http://projects.lemuria.org/projects/ttt/wiki).

To make roads look right on a height map (eg. not just a general smeary gray streak on the terrain), these need to be modeled separately. The Unity Asset store contains some tools that can generate the road geometry for you and will also automatically flatten the height map under the road so the road will sit properly on top of it.

So using Unity (not necessarily creating the initial height map in Unity, but using Unity's terrain system) is better from a workflow and flexibility point of view.

If you're shooting for the absolute best in quality, modeling the environment in Maya or another 3D suite will yield superior results, however. You're not bound to a grid and can freely create overhangs, tight canyons, bridges, etc.

Thank you very much! Would using terrains modelled in maya be heavier in size compared to that built directly in unity? This is cause being a web based game, size is a major factor in the country we are targeting to put this up.

thanks, Rajiv