Generally speaking, unless you have a desire to own or be short the underlying stock, you're better off reselling an option that is in the money. In the end the net profit comes out about the same both ways. For instance, if you have a 50 call on a stock that is trading at 60 and you paid a $5 premium for the call, your option at expiration is going to be worth $10, and you'll be looking at a $5 per contract profit. If you resell the option you'll pocket the $500 profit. If you exercised the option you'd be buying the stock at 50, which you could turn around and sell on the open market at 60, for a 10 point profit. However, you paid $500 for the option originally, which means that your net profit on the stock is still $500.
Most option traders close out their option positions and take their profits, rather than deal with exercising them, which adds no profit to the trade.