unreal : for simplicity but assets are harder to come by and you will have to do a lot of them your self unity : more wouldnt say harder but a lot more typing and more people seem to use unity and if you look in the right places assets are easy to come by and they are never ending
there are a few other game makeing programs around but never used them i myself use unreal engine but do use unity from time to time there plenty of videos around and a lot of on line courses some good and some bad
depends on what sort of thing you are wanting to make and how many hours you have as its not a 5 min job but very rewarding if you spend the time