Thh only thing you have to keep in mind that girls go into heat which can be a hassle whining male having to guard and often separate them during the critical period.
I have several basenji friends that have 2 even 5 boy´s and it works as they are of different ages puppies are integrated in to the pack when they are less then 12 weeks.But it takes a strong leader males rarely fight to kill more to show who´s the leader and when the other gives up they calm down not so with females they can be really nasty.
Are you going to show them and maybe in the future breed then yes a girl but if not i´d choose a boy as it´s cheaper to neuter a boy then sterilize a girl.Especially as you have to let her have one heat before surgery maybe it´s different over there.And as I said before you can have boy´s together that aren´t neutered.But as they´ve mentioned before go with your breeders recommendations.
In the US, price is usually the same for a spay as it is for a neuter…. and usually people opt to spay before the first season in the US.