While both male and female make wonderful pets, their personalities are like night and day. You should definitely consider the following when picking out a rat that will best suit you.

Male
Male rats are larger in size, have a coarser coat, and are lazier than females. A male rat will be more prone to sitting on your shoulder and enjoying a walk around the house or backyard with you, laying on your lap while you watch a movie or work on the computer, and most love a good head-scratch. Like male dogs, male rats will scent mark (only 2 or 3 drops of urine, but something to think about) but this can be controlled if they are neutered. Their cage may need to be cleaned more often if they are not neutered, but leaving a small amount of the soiled litter in the cage after cleaning may reduce this.

Females
Females are smaller, leaner, softer, and a whole lot more hyper than males. Females prefer exploring to cuddling, but are fun to watch run around and play games with. Females may need more things in their cage to climb on and play with, while males should have more soft things to lay in or on. Females are more prone to chewing things up quickly, though males will too… just at a slower pace. Though females are typically very active, some may slow down when they get into their “senior” stage.