I prefer bitches for the purely practical reasons that they don't usually cock their legs on everything, and there is more tummy for rubs.
My bitch was desexed at 8 weeks. She's a year and a month now. She has never marked over another dog's mark -though she likes a good sniff there. She is very loyal to me, and freaks out on walks when she doesn't know where I am - which I use to my advantage. She's an independent thinker - recall isn't always reliable at the moment. Especially when hotdog sausage is involved. She's extremely outgoing, loves to greet every person and every dog and would greet cats if they didn't run or weren't so grumpy. Likes chasing cats that run. And she's a big sook. Loves cuddles and pats, and leans on me or anyone who will give her a pat. And she loves belly rubs. She's very non threatening with small children, but barks a lot at men who look at her wrong or try to reach out to pat her.
So all that was to try to say that the personality attributes that some of you assign to the different sexes don't seem to apply to my dog. Nor have I noticed that kind of gender specifics with other dogs I've lived with.
I had quite a few people say I should get a male dog because I'm female and that will be a stronger bond but hasn't actually worked reliably - some dogs get along with me and some don't and which sex the dog is doesn't seem to have a lot to do with it.