Your comments

On a model-driven form, having a dropdown to select a value from a short(ish) predefined list (e.g. provinces/states) is a bit more intuitive/cleaner and has fewer clicks than a lookup. "Then why not use an optionset?"  Good question, using a lookup references a table that an end-user can manage within the context of an app (add/remove values) instead of modifying the solution/publishing/deploying/etc.  This is actually a feature within portals (render lookup as a dropdown) and I have used it on a number of projects.  Hope that helps!