This is one of my other soap box subject... There is absolutely NO difference between dogs and bitches as far as trainability, temperament and husbandry requirements go.
Bitches are not sweeter natured than dogs - they are all JUST THE SAME. Very, VERY generally speaking... dogs tend to be more loyal and bitches more intelligent; although some smart bitches might try (successfully!) to outwit their owners - you have been warned!
Please do not buy a bitch and then let some silly but well meaning Vet persuade you to get her spayed for no good reason - it is certainly NOT "the kindest thing" to do.... Keeping her away from sexually active male dogs for a couple of weeks is far, far preferable to major invasive surgery which can change the bitch's whole demeanour, coat and temperament. Not to mention the urinary problems which can sometimes result.
I personally, again, don't approve of unnecessary castration either. Train the owners - don't perform surgery on animals just because of inadequacies in the owners ability to keep their dogs under control. [Always remember that it isn't the dog's fault he is untrained]. UK Vets may claim that spaying a bitch can prevent things like pyometra and tumours as well as those unwanted pregnancies... why not take out the poor animal's eyes and remove any chance of developing cataracts? In some European countries the routine neutering of canines is very much frowned upon and considered "unnecessary mutilation" by their individual Veterinary Associations. I'm with them...
And what of the boys? If there is a medical or temperament reason to castrate a dog then fine. But why oh why oh why march the poor chap to the Vet to have his bits snipped off at only six months old?? He hasn't even started to behave as an adult male might behave and I stress it's only MIGHT. Very, very, very few male dogs become a problem with too much testosterone. Correct training overrides any desire to fight all comers, check out any bitch in the district or mount anything anyway just in case. I challenge any Vet to justify this practice. Their main reasoning is to prevent unwanted puppies but isn't it down to the owners to control their dogs?
Agressive dogs are not made more gentle by castration. A lot of agression can actually be learned behaviour, so chopping off his bits will not make any difference. It will, however, make him not smell like an entire male so more likely to be mounted by entire dogs.
BE WARNED... Neutering takes away the pet's identity. When canines meet they sniff each other's nether regions in order to check the other's sexual status. Are they a male or a female? If female, are you in season? If the animal is neutered they smell of neither- so the dogs think, if in doubt, try mounting him OR her anyway!!!
When the poor animal at the bottom objects to being jumped on by another strange dog, by snapping/snarling, even biting, it is he/she that is accused of "being nasty" and all the poor animal was trying to do was protect itself.
It is also scientifically proven that a bitch's temperament is adversely affected by being spayed. Not hard to realise why, is it? Consider a young woman having a full hysterectomy with no back up HRT? She could easily turn from being a gentle soul to being a screaming witch.
The neutering of any dog before it is physically mature is abhorrent. You wouldn't do it to a child, would you?!
BUT PLEASE don't let me and my giant soap box prevent you doing whatever you believe is best for your own circumstances!