If you have the space , a sump filter is one of the best filtration you can set up. However, note that sump filtration is only useful in high bioload tanks (ie monster fish, predatory fish, messy eaters etc), otherwise, it is an overkill (Well you can never have too much filteration, but if you don't have a high bioload, you can use another filteration and instead use the space for another fish tank!)
The best advantage of sump filter is that you can increase your tank water volume greatly, depending on the size of your sump. With a large water volume, there is less fluctuations in water parameters and the water is more stable. You can also house a great amount of biological media for bio filteration.
Sump filtration has other advantages, for example you can set up a wet-dry filtration in the part where water enters the sump by filling it up with bioballs. Also, you can change water using the sump or even grow plants in the sump to soak up excess nitrates.Maintainance is also easy since the mechanical filter media (ie filter wool) is in plain sight so you can easily see when it needs to be cleaned or changed and if maintainance is needed you can easily do it without have to turn off the power or meddle with covers/clips/clasps.
Electricity wise, sump systems can hold the most amount of biological media for bio filteration while using the least electricity. In fact, a sump can use the same amount of electricity no matter how much bio media the system houses.
The one important thing to note is that you should be careful of the piping work if you are setting it up yourself or making modifications. If you drill a hole at the bottom of your main tank for the water to drain out to the sump, you should use a long pipe so that water drains out from the top of the tank and not from below. This is so that if the pump is to malfunction you wouldn't have most of your tank water drained out. If you find a pipe unsightly, you can also board the sides of the holes up with acrylic or glass so that glass overflows from the top. You can then fill the inside with bioballs so that the space in used for wet-dry trickling effect.