PIA would be best. I do not know about KSA-PAK route, but have flown from US-Pak over a dozen times, and have always chosen PIA. People have also tried Emirates from USA to PAK, its nice, but the Stop over in UAE made their journey long.
PIA has nice aircrafts, good service and staff that is also Pakistani. The foreigner staff usually is apathetic and many do not like flying in and out of Pakistan, so their attitude also is reflected in their service towards Pakisatnis, so why not chose PIA, where the aircraft and services are well above anyone else's.
In USA, the local American airlines like UNITED, American Air, Delta, etc. all have the WORST service. They DO NOT even give you food, while flying within US, they only give you a small packet of peanuts on domestive routes, which can be upto 6 or 7 hours long if you fly from New York to California.
Now they are SELLING Lunch packs to flyers, using the credit cards, the airline business and their service has gone down the drain in US and it SUCKS big time. Many airlines have filed for Chapter 11 Bankruptcy, meaning they are running on Government's support.
PIA compared to most American Airline wins in service.