I have had both male and female dogs since I was a little girl, and lots of them were not neutered since it was not a common thing to do when I was that much younger than my current "26" years old...
...but, none of my boys, large breed or small, ever marked indoors and I never out-trained the behavior from them. My Yorkie-Poo rescued when I was young teen was never neutered, I had him at least 10-12 years, and he never marked. In fact, he only 'went' along the fence line in the back yard...his choice. He was very well trained, but there was never any reason to teach him not to mark.
I have also have lots of girls, altered and unaltered, and none of them marked indoors either...again, no special training. The only babies I have had 'go' indoors were potty training accidents...which are MY (the owner's) fault for not reading THEIR signs, not being on top of the situation, not being home, etc. and are no big deal...sop mop do better.
I currently have both male and female Yorkies who are each 2 years old. The male squats...does not know to lift a leg. The girl squats, and like some of my other females, lifts a leg a couple inches off the ground...so cute!
Both are completely devoted to Mommy...pasted to me...little shadows, and buddy up to DH, and snuggle with him, too. The differences are personality-related...the girl, who we've had 3 months less than the boy...does not let me out of her sight, but the boy will sometimes delay following me. Both have their own internal timer...like "1 minute" (I always tell mine how long I'll be gone) = "how dare you leave the room without me!
" sometimes. Both are lap sitters, bed snugglers, car riders, and LOVE THEIR CLOTHES!!! Both like getting all prettied up, too. I'd take another boy in a heartbeat...
If you have fallen in love with a boy and do not get him, you will be MISSING OUT on one of life's great treasures!!!