I have flow Austrian in C quite a number of times longhaul and short haul.
There seats as pointed out are pretty antiquated and I find them no more no less comfortable than LH seats. They are not lie flat and not great for sleeping in. They dont however give you much time to sleep if you want to partake of the entire foody experience which really is excellent including the floppy hatted chef in whites. Coffee service is really good; big frothy viennese coffees. IFE is poor. I guess it depends on price at the end of the day: If no diofferent choose swiss for the seats; if Austrian cheaper by a couple of hundred i would go with them.