If web systems have a performance penalty it will be because of inadequate bandwidth. But think about what the Web is being used for. The universal access and exchange of the Web is really a clever digital use of interactive telephone line technology. There was a time when the only local and long distance carrier was Ma Bell. Open systems create competition.
Competition creates innovation.
Innovation results in more choices, great products and reduced costs. That's why proprietary systems are dead. They are both costly and limited in function. Proprietary systems are great when they're the only option you have. But once an Open System is available, and the Internet is both Open and available, the few costly advantages a proprietary system might have are sure to fade fast.