Winter is better, cus they have long pants on that will absorb the pee so it wont get on your carpet! And, in the summer, they are busy playing and do not want to stop to go potty. I agree wit the previous that pull ups are a waste of time and money. Boys are not hard to train. I trained 2 of them, both within 2 days of the day I started. Get him excited...talk to him about wearing big boy underwear. Tell him "we are going to go to the store tomorrow to get your big boy underware", then take him, have him pick them out, come home, and put them on. Dont wait around, cus it will lose the excitement. Tell him if he feels like he has to go potty, then he has to tell you. Both of my boys peed several...like 7 or 8 times the first day. You just have to remind him (do not get angry) that he has to tell you so he wont get all wet. Day 2 will go better (put him on the potty first thing). My sons had 1 or 2 accidents. 3rd day even better. You have to ask several times throughout the day if they have to go. I used the doughnut that went on the toilet for my first one. The potty chairs were too small. But, with my second, I just turned him backwards on the potty. It works wonderfully. My 3 year old still sits on the potty. I would sugguest that you have them sit as long as possible to avoid messes. My 5 year old stands, has been for about a year, but he has pretty good aim. I would suggest also that before you buy the undies, to put him on the potty every night before bed and every morning before he gets up for about a month or so. So he is aware of what he is supposed to do on there.
Hope this helps!