Stick to Canada, because you will regret your decision after wards.
1) Number of Air Force officers belonging to Engineering branch once sent for MSc degree or Phd degree to USA, Canada becomes unfit for Pakistan Air Force on their return. Reason behind this is that they are able to see their worth in first world countries as Engineers where as in Pakistan Air Force they have to serve in remote locations with less salary and then they think they are being under paid and deserve more in life.
2) Life in Pakistan Air Force is tough and somehow they feel that they are being mismanaged by Pakistan Air Force on their return.
3) People can easily settle who leave third world countries for first world countries but those who return from first world countries to third world countries can never survive. These are the facts.
Selection criteria in Pakistan Air Force is very strict and even once you will get selected then only 12- 30 % of Cadets makes it to GDP pilots and maximum number of them are grounded once they are officers and sent to serve in Ground branches of Pakistan Air Force.
Dear, I have successfully graduated from system as Avionics Engineer 10 years back and this is a valuable information which I have shared with you.