I have both - 2 boys and three girls. IMO, it's true when they say that boys are more affectionate, and girls are more ... well, "moody". Now, don't get me wrong, every dog is different, and my girls just happen to be very affectionate too, but there's just something about a boy with his Momma. Mine cuddle more, and follow me close. My girls are more independant (women do have their own minds, and can be stubborn at times)
My girls are also dedicated to my husband, so I guess that saying is true too!
When I had to choose my first yorkie, I had the same dilema. I went to see the litter, and Shadow was one of 5. That day, he was in the playpen with his siblings (who were all sleeping when I arrived). Shadow was the first to wake up, and as soon as I picked him up, he started kissing me like crazy. At that moment I had decided on a boy. So, maybe one will make the decision for you! Either way, you're going to fall in love!