Hello JohnTrue,
In my own experience, "mobile" air conditioning units are a good option depending on your requirements.
If you live on your own or just two people and you don´t spend much time at home, let´s say you´ll just use the air conditioning before sleeping or while having lunch at home, a mobile unit could be a cheaper and still convenient option (of course buy a unit with a good relation quality-price). I did that for sometime and it was OK.
But if you are more people, using more espace at home at the same time or you really want the change of temperature to be quicker and/or for more time (hours or the full day), then one or more wall mounted units could be a better option. Check also quality-price. And of course in this case ask for Technology "Inverter".
Regards