Getting it right the first time.

[eluser]auximage[/eluser]
In your opinion, when defining models for a new project, do you find it best to get more granular or try to keep your models more 'grouped'?

Case in point; while designing a code re-write in a MVC framework I have a group of systems that I interact with. While all of these are part of a 'larger' overall system, the way I interface them is essentially the same (curl requests). Would you think breaking each system out into it's own separate model makes more sense, or would one overall model be best to deal with them?

This has been nagging me because I have no way to see what will come down the development pipe in the future, and don't know if it's worth it to have 3 small models, or one larger model.

What would you do?