First of all, easy to use. I have been using ArcGIS for almost 7 years now and I can tell you that people love it's simplicity and how to build simple maps and analysis.
I have been tracking and also using QGIS for almost 3 years now and as other have pointed, QGIS is getting closer on funcionality, but still "ESRI" is printed on peoples mind.
ArcGIS has a solid documentation, large use base and support for old products that most of other companies cannot provide. They have been investing in new technologies and spread of new concepts (which may be something or not - check out GeoDesign).
QGIS is a very strong candidate for a replacement of ArcGIS. There is one specific project, for a municipality here in Brazil (a large north capital) where we were able to stick with QGIS and they seem to be very happy with it. Customizing it is another point, but it doesn't seem hard - everyone just need to "get used to it".
One point in favor of ESRIs tool is its native cartographic output which is still the best, and looks like it will be for some years.
EDIT explaining the native cartographic output comment:
Well, most of GIS softwares nowdays can export to a different format, such as PDF and SVG, to be edited outside the boundaries of GIS scope.
I've heard that many many people uses FOSS GIS software to generate the basic layouts of their maps, and then change to something like Inkscape and refine the look and feel of that map.
Natively, ArcGIS has the best cartographic control and output of all. It has extensive labelling features, symbol creation, it's has many features of a vector graphics software.
Thats what I meant as native cartographic output :D
As Luigi suggests, you can have a look at the API documentation, specifically to QgsVectorFileWriter::writeAsVectorFormat, and realize you're just missing one parameter (from the docs):
bool onlySelected = false,
It says that the parameter onlySelected is of type boolean and is false by default. This parameter is right after the driver name. So, calling the function this way:
_writer = QgsVectorFileWriter.writeAsVectorFormat(i,r"C:\Users\XYZ\Desktop\NewFile.shp","utf-8",None,"ESRI Shapefile", True)
will export only the selected features from your layer.
Best Answer
Read the 'importing data' section of the manual, found on page 54. Here's the manual: http://www.cetaecoresearch.com/Software/Pythagoras/Pythagoras_manual.pdf
It states that you can import excel data. I recommend exporting your GIS data to csv, open in excel, save as excel doc, import to pythagoras.
If you have programming skills you may be able write a script to convert GIS data to the pythagoras metafile format.