Hi motorsep - SketchUp is more oriented towards architectural kind of boxy-form modeling. If that's the kind of thing you need to build then it could be a good fit for you.

If the models you want to build have some more curved shapes to them, then MoI is usually a better fit for that since the method that MoI uses (called NURBS modeling) can make true curves instead of only line segments and polygon facets.

I would encourage you to spend at least some time experimenting with both yourself though.

- Michael