AOA...I recently bought both cars so i think i can give u good advise here. My Belta is 1000Cc 2008 model. No problem of spare parts. Also, the used spare parts markets in Pindi and filled with belta parts. Car is very nice. Very good interior and exterior finish. In close comparison between the 2 cars, swift does not have much trunk space, but has lightening fast pickup. Interior is bad finish, as all suzuki cars do. U might experience some rattles also.
Simply put, my belta which is 2008 model and had 50,000 km on it seems to be in better condition than the swift which has just been driven 5000 KM will now and is 2012 model.
But in your budget of 13 L, i dont think u will get a very nice 1.3L belta.
I hope this helps