Lets say you have $100,000 available and on a Sunday the Saudis announce that they will cut pumping oil by 1 million barrels per day. You can be 100% sure that on Monday the price of oil will go up quite a bit.
Now here are the differences between the EFT and Mutual Fund.
If you put in a 100K order in an Energy Mutual Fund the price you'll get it at will be the price at the end of the day at closing on Monday. So if there's a 5% increase you don't get it at $100,000 you get your shares at $105,000.
With an Energy EFT you can put in your order on Sunday and get your shares at the Monday open for $100,500 or whatever then ride it up all day then sell at 3:59 EST and make $4500 (4.9%) profit or whatever it is.
With the mutual fund you are always a day behind and it's recommended to never day trade a mutual fund or trade it at all.
I've simplified this quite a bit but it will give you a general idea what the differences between the two are?