I fly about 15-20 times a year. I've seen quite a few: Yemenia is horrible! I even flew Iraq Air once--the economy seat reclined 90 degrees--or until it hit the person seated behind!
PIA is pretty bad. Off-board service sucks and then you have the risk of extra checking at international airports just because of the track record of PIA.
On long distance flights, always check the seat layout. Qatar uses 3-3-3 on their 777. Etihad changed to 3-4-3. Emirates has one of the most cramped 777s. On ultra long haul (12hrs+), A380s are comfortable but boarding, disembarking and getting your luggage is a pain. The smaller the plane, the better for short flights. I also hate Dubai airport. The walks are too long. On the other hand frequent flights and flights to less frequented airports is a major convenience.
At the end of the day, always choose the cheapest unless it's PIA and the next best isn't really that much more expensive. You also need to consider baggage allowances. To Europe, PIA/Emirates/Qatar/Gulf offer 30Kgs. Turkish does only 20kgs.