Fuel Average - I never had experienced driving yaris in rural areas but my assumption is 1.6 will give you around 8-9 fuel average and yaris can give you around 11. In lahore i am getting 13.5+ in summers and 14.5 in winters.
Drive and comfort - Yaris shocks are too soft and they tend to bend more as compare to corolla. I think corolla will perform better in rural area as compare to yaris
Plus yaris front shocks have some weird dhaak sound when you hit any pothole and they are more pron to produce noises. I recently asked dealership to thoroughly check the shocks as mine was making noises. They applied grease on the bushes and now they are fine
Performance - Both will perform more or less same in this terrain, based on my experience both cars have same 0-100