What Reasons might have Genne have had for wearing Phineas's Clothes?

Gene and Finny have an odd relationship. Both are co-dependant on each other in an unhealthy way. They spend much of the book in competition with each other while, at the same time, trying to be like each other. Even after the accident their relationship borders on obsessive. Many critics feel that there are homo-erotic undertones to them. In any case the most compelling argument for the clothes is that Gene wants to actually inhabit Finny's space. Yes, I'll say it, he wants to be Finney. This does not sound so farfetched when we consider the very obsessive co-dependant relationship of these two boys.