I don't know why someone downvoted this as this is a questions forum, but the difference between the 2.4GHz and 5GHz bands would be that:
2.4GHz covers a larger distance and travels well through walls, but has slightly reduced data transfer bandwidth;
5GHz covers a smaller distance and travels poorly through walls, but has a slightly higher data transfer bandwidth.
I recommend testing them on your own to properly learn the differences and see for yourself, but that is the main difference. Use the 2.4GHz band if you'll be in another room far away from the router; use the 5GHz band if you'll be in the same open area as the router for a slight increase in data transfer from the router to your computer. I use the 2.4GHz band myself, btw.