Terrain Stuff

I want to do an earth-simulation type program, just where I model my property or something, in Direct 3d. Of course I''ll do more than just that later, but for now I''ll start with that. I''m very new to this. My main question is about the terrain: Should I a)make it as a vertex buffer and apply a texture to it, in-game or b)model it in a 3d program, export it to .X with texture maps included. Which would look better? Which would be easier to use? What about render time? I''d test these myself, but my export program won''t support texture-map exporting ''til I buy it. I should probably read a good tutorial or something... Thanks!