Quote from ChaosNSX:
Its actually easier to trade a well managed 100 share intraday portfolio up to $100 a day consistently than it is to trade one 100 share position at a time and by the end of the day end up with 100 dollars.[/B]
i don't know what's "easier" but a portfolio offers significant advantages over a single instrument, such as: diversification, correlation between instruments, and market neutrality.