I've used both so this is my opinion. I like the top opening if your a live feeder because the live pray tends to run in to the opening of a side hole hide if the snake doesn't get em fast enuff. One thing I dont like about a top opening is that the size of my biggest girl in her rack she doesn't have enuff hight to get into the top. Other wise theres no real differance. hope this make sence and helps.