The front end is more concerned with the visual and implementing the appearance of a web site (caveat - all my reference points are from the perspective of the web dev industry - it’s where I’ve worked for years now. Other software development will vary). Front end has a lot of art as well as science to it, and usually a lot of trial and error. A number of front-end developers I work with started as graphic designers (even a few fine arts majors) who had opportunities to learn front-end coding and realized that was their passion. Back end is more structured, technical, and logical. Which one is more “difficult” is going to depend on how your mind works. Computer science majors tend to be much more likely to be back end developers than front end.