Apple Macintosh or Microsoft Windows ?

When asked to help with buying a new computer I am sometimes asked why I suggested Microsoft Windows over Apple Macintosh or vice versa.  I will have taken into account the client for whom I am suggesting (current knowledge, aptitude for learning new interfaces, financial resources available), the form factor and current market trends (at the time of writing iPads dominate the tablet market) and other such changeable factors, but the following shows the unchanging background to the decision. 

All that follows is predicated on one main fact: Apple maintain a proprietary control over their computers: hardware, operating system and programs.  Microsoft retains control over the Windows operating system but the architecture is open so anyone can produce hardware or programs for it. 

I hope the above appears to be presented from a neutral perspective. I am happy doing my best to help with either platform, but as well over 90% of my clients chose Windows I generally have less research to do when presented with a Windows issue.