I think the main advantage of team working is that you have more options to choose (yours and your teammates). I've done a couple of solo projects and took some horrid decisions that, had I had a parthner, he'd had strangled me. When in a team, you analize your decisions better, because you want your mates to understand why yours is a good choise. You also learn from the experience of your mates, who have solutions different to your owns. And in the end, you end taking the best choises your team can come up with, instead of only what you can come up with. Also, when actually programming, you can share good practices among your team. This improves the quality and efficiency of everyone's work. It's like being capacited all the time. Also, having the need to make your project understandable to the rest of the team, you document your work more carefully. This means that if (when) you leave the company, someone will be able to mantain your project with less effort (meaning less time and costs for the company, if to convince your boss).