Apart from the obvious genital difference, there are numerous small differences between male and female guinea pigs. These myriads of differences affect which gender works best in the space you have and with your household.
The Size Between Male and Female Guinea Pigs
In general, male guinea pigs are bigger than female guinea pigs. Males also tend to weigh more, though not by much. This distinction affects how much space and food guinea pigs need to thrive, as well as the outcome of many fights.
The Living Arrangement Necessities
Generally, you can house female guinea pigs together for their whole lives. There will be some initial bickering while the pecking order is sorted out, but once that’s settled, female guinea pigs tend to live together peacefully. They can even successfully cohabitate in a smaller area than males.
Male guinea pigs differ from female ones this way. During the first several months of life, male guinea pigs are fine living together. However, this changes once they hit sexual maturity. It does not matter if there are no female guinea pigs in the house; the vast majority of males will need to be housed in separate areas. Otherwise, you will be treating bites constantly.
Additionally, gender tends to affect how often you need to clean the cage. Female guinea pigs tend to be less inclined to throw food everywhere than males. Additionally, males tend to secrete more musk that gets everywhere. Be prepared for that since there is no fix.
Male guinea pigs tend to be both noisier and more outgoing than female ones, especially when you first bring them home. Females tend to need more of a warm-up period for humans. You may notice your male guinea pigs are more likely to talk when you enter the room too.
Of course, personality is an individual attribute. You may have a super outgoing female who eats out of your hand from day one and greets you every time you open the door. You may end up with a super mellow male who never fights anyone or gets territorial.