Thank you for the feedback. As far as the barcodes are concerned, with the current implementation in XAML rendering they are raster images, while in PDF (the non native print) they are rendered as vector graphics. We're aware of the difference in both formats, so we will see how we can improve the image quality in XAML/XPS formats.
As the fix will take some time and image quality is important for barcodes, we would suggest using the non native printing.
Please, accept our apologies for the inconvenience.
the Telerik team