The million dollar question, what sex cat should you adopt? There is no right or wrong answer, each gender has pros and cons. In my experience, I have found personality to be more of a factor. Some females are friendly, some aren't. Some males are friendly, some aren't.
There can be some differences between entire cats compared to desexed cats.
Males tend to roam further afield looking for a mate. They can also be more aggressive over territory and get into more cat fights as a result. While both male and female cats spray, males tend to do so more often than females.
Females go into heat from around six months of age and repeatedly come into heat until they are mated. She will do everything in her power to escape and find a mate, calling at all hours of the day and night. We had a female go into heat ONCE, that was enough. She was spayed immediately afterwards.
I have found that desexed cats have more similarities to each other. Spraying is reduced in both, as is territorial aggression (although it remains in some cats). Both males and females stay closer to home as they are no longer interested in looking for a mate.
I have found my male cats to be a little more affectionate and placid than the females. But that all comes down to what you, as the pet owner wants. Some people want a cat who will lie on your lap all day long, others prefer a cat who is a little more independent. If there is a difference in male and female cats, it is very subtle, and personality is a much better indicator.
It is sometimes said that female cats are better at hunting than males. One theory is that female cats think us humans are fairly inadequate when it comes to hunting and they bring us mice in the hope that we will learn how to become hunters ourselves. Maybe that's why people think females are better at hunting, they are more likely bring home their "trophies"?
I've known both male and female cats who have been exceptional hunters so am not convinced one sex is better than the other.
I think when bringing a new cat into the household, current cats should be factored in. Do you have a dominant male cat? If so, introducing a kitten, or a female cat may be better. But there are no hard and fast rules. I do have experience introducing an adult male into a home with an already dominant male and it was somewhat of a disaster. The resident cat never accepted the newcomer and we lived with both cats fighting and spraying (despite both being desexed) for many years. I currently have a slightly less dominant adult male than the previous one mentioned above and have just introduced quite an "in your face" kitten, and while a little miffed about it, he has begrudgingly accepted the new kitten. I think there would have been fur flying if I had brought home an adult male. But, some cats are more laid back and will readily accept a new addition, adult or kitten, male or female. I had an adult male who was very welcoming to new cats. He wasn't overly dominant, though.
If you are choosing a purebred cat, you can get a "general" idea of what to expect. Obviously, not all cats will fit the personality description of the breed, but it can be used as a guideline. I also like to let the breeder know what I'm looking for, ie; "I really want a smoochy boy" or "I love talkative cats", or "I prefer a cat who doesn't need to be on or with me 24/7". They have been with the kittens since birth and will be able to narrow down which kitten/s fit your preferences. Some people love smoochy cats, other people prefer more independent ones. I personally sit somewhere in the middle.
Even if you are adopting a cat from a shelter (great idea), the staff should be able to help you find the perfect cat or kitten to match your requirements.