Whilst Bomber Command sustained the highest number of casualties in the RAF during WW2, it also had the largest number of personnel exposed to risk. In "Right of the Line" by John Terraine there is a table worked out by the Air Member for Training in November 1942 which shows the percentage chance of survival for 1 or 2 tours by aircraft role:
Type of Squadron - % chance of survival - One Tour - Two tours
Heavy and Medium Bomber - 44 - 19.5
Light Bomber - 25.5 - 6.5
Day Fighter - 43 - 18.5
Night Fighter - 39 - 15
Long Range Fighter - 59.5 - 35.5
Torpedo Bomber - 17.5 - 3
Heavy GR Landplane - 71 - 50.5
Medium GR Landplane - 56 - 31.5
Light GR Landplane - 45 - 20
Sunderland Flying Boat - 66 - 43.5
Catalina Flying Boat - 77.5 - 60
Fighter Reconnaissance - 31 - 9.5
Bomber Reconnaissance - 42 - 17.5
The light bomber figures reflect the high losses of Blenheims and Battles in France and Belgium at the beginning of the war. The heavy bomber losses continued throughout the rest of the war whilst the Torpedo Bomber loss rates probably diminished with the introduction of the Beaufighter and Mosquito into anti-shipping strike.