ALL children are different in temperaments and abilities so it makes sense that even within the same family they will train differently. I personally haven't found that it matters whether they are boys or girls. My first child trained easily, he did what mama said every time so was easy to train, my second trained herself at 18 months, she was done with diapers day and night, but she wouldn't poop in the potty or toilet until she was 3, when she found out her "Tata" (grandfather) used the toilet, and my third, he was like your son, "Why should I stop and go to the potty/toilet, when I can do it in a diaper?" ; )
So, how serious are YOU about wanting him to train? If you are committed, then you need to take him to the potty at regular intervals, say every 30 minutes or so until you know the times he usually goes, don't ask him if he needs to go or wait for him to stop what he's doing and go, you need to take the lead, to train him. Set a timer so he hears it as well as has you telling him as you take him that it's time to go potty, a double reinforcement. There's even "potty timers" children wear on their wrists, they look like watches, my friend got one for her son and he felt so important, he'd announce to everyone, "It's time for me to go potty!" as he ran to the bathroom ; )
At 3 he is possibly past the potty and will relate better to the toilet, unless he is a small guy. My guy trained at 27 months, and used the potty most of the time rather than the toilet, but once he hit 3 it was "I use the toilet!" and the potty was history. Make sure he has a sturdy step stool to help him get up and down from the toilet, and to place his feet firmly on when he pushes to poop.
Rewards did absolutely nothing for my guy, for some kids the act of being trained is the reward in itself, it was with him, he's an "I do it!" guy. You can try them and see, all kids are different.. a friend of mine was happy to receive his books, stickers, etc., to try with her son, but they didn't work with him, either. Poop training was different, though, he held it and I had to go online for help in getting him to poop in the potty, and what worked for him was a "power incentive," something you the parent retains ownership of and the child earns 30 -60 minutes of use of it, that way the incentive stays an incentive unlike when you give him something outright. This is the site, it helps with all potty training problems:
http://www.rogerknapp.com/medical/pottytrainingrefusals.htm
Toss or give away the diapers if he isn't in underwear yet, and don't go back. Put him in cloth training pants (I used Gerber), along with loose shorts and/or pants, to make it easy for him to get them up and down. Use covers over the undies, or cloth training pants, so he can feel the wetness yet keep his outer clothes dry, and know he needs to go or needs to react by going to the toilet the next time. It may take some time for him to recognize what his body is telling him but he'll learn. Most people say a child needs to be able to tell you when they need to go, I found that my guy isn't one to share what he feels is private information, he just goes and does his thing and asks for help if he needs it, like when we are out and about and there's no stool to get on the toilet. I don't mind, I like his independence! Teach your son to wipe, flush and wash his hands, it won't be perfect for awhile, the point is to get him doing it all since it's all part of the potty training process.
Stay consistent with him, reassure him he can go back to playing when he's done going potty, and have Dad take him in the bathroom when he goes so he sees it's a natural thing, boys love to imitate Dad! Encourage him, tell him he's a big boy and can do it. Remember that night training is a misnomer, there is no such thing, A child will stay dry through the night when their body is ready, as your daughter and my little guy did, for some kids, though, it's not until they are 7, 8, or even later. If this is his new way of life he will hopefully train by his birthday.
