Probably a noob question about my modeling method

First off, I feel the need to mention that I’ve picked up blender only a couple of weeks ago, and I’ve been trying to learn by doing my own stuff, trying to avoid tedious tutorials. Still, I decided to watch a few and I’ve noticed that most people try to model everything out of a single mesh, while others(especially me) combine and intersect different objects to create their models. (anyone who’s played Spore knows what I mean).
Here are the tutorials, maybe you can get an idea of what I’m talking about:

Here everything is extruded out of the main mesh, making most of the building a hollow shell;

while here he makes the doors, windows, roof, etc out of separate cubes that are intersecting the main piece.
My question is, is it “wrong” to do that? Should I try to avoid using multiple objects on a single model? I think it raises the vertex count, but I find it more confortable than extruding everything.
Thanks for your time guys.

Objects are manipulated in object mode, you may and usually have multiple object types. Object data is manipulated in edit mode, one object at a time. What that data is depends on the object type. For mesh type objects it means mesh (vertices/edges/faces), the geometry which the object consist of.

Three options for model construction:

  • multiple objects
  • one object, multiple unconnected mesh parts
  • one object, connected geometry

You can use whichever you like, or combine, depending on the situation. It’s recommended to keep the geometry unconnected (as separate objects or separate geometry within one object) for real life objects that are constructed with separate parts, unless you know the reason to connect the geometry.

I think the question, as asked, can’t really be answered because it doesn’t provide enough context. As JA12 points out, it depends on the situation. In other words, how are you going to use the model? Are you going to 3D print it? Are you going to use it as an asset in a game? Are you going to render a still or an animation? Those kinds of things will help to determine how you construct the model.