>>4216671If you have two lenses where it's the same focal length, same max aperture and essentially same quality glass then really the only reason I can think of is how compact you want your camera to be and also maybe how being mindful of how expensive each lens is. Maybe you despise tripods and want your camera to be as light and hand-holdable as possible. Glass size doesn't necessarily mean greater quality as it would be more expensive I imagine to have the same quality glass as a smaller lens but larger size. There is sometimes also the fact that flash sometimes can't get over the longer lenses so a pancake in this case would be better as you aren't at risk of the lens shadow entering the shot.
I personally would just stick to regular lenses as I don't have baby fingers and also like my lenses to have lots of controls on them rather than let the camera do all the work, but then I shoot film so what do I know.
