Different Corals are adapted to different types of currents. The reason why you need so much current is that food particles such as bacteria, plankton and other organic stuff in your tank become more readily available when you get things flowing. Just like the corals grow and change shape, so too does the reef itself resulting in currents changing. So just as we struggle to prevent dead spots, nature does as well. Only it’s a hurricane or tsunami that rearranges the coral. Be prepared to experiment with currents, paying careful attention to how the coral responds. Be willing to thin your corals out if necessary to allow more flow.
There are many ways to go about creating good water movement a reef tank. Many products and methods can be used: Closed loops, power heads, wavemakers, eductors and spraybars to name a few. The key is not to have any dead spots in the tank. One of the problems we face in our tank, is that certain areas get less current over them as corals grow. It's important to periodically check the coral, top to bottom, to make sure the coral is getting good water movement around it, especially near the base. Something that becomes progressively more difficult as the tank matures and corals grow into the flow cutting off water flow to areas (and corals) behind them.
In the end, current is current, just as wind is wind. Each device used to produce it has advantages and disadvantages (purchase cost, operating costs, maintenance and reliability to name a few). Generally the less sophisticated your equipment the better. A wise point with any pump or powerhead; it's easy to not clean them regularly - and every pump will last longer and possibly run better when kept clean.
It is very important to differentiate between flow vs. velocity. Many think that just because the velocity is high, that they are getting a lot of flow (gph). This is a common misunderstanding. When using high volume pumps (closed loops and streams for example), a good way to manage a lot of flow is to bank it off the glass. Bouncing the stream off of the glass is good for breaking up the stream of water, so that it isn't just one direct blast of water hitting the corals, but it doesn't eliminate the need for some type of alternating current device. What's important is that you don't want direct flow from a pump or powerhead hitting your corals, or it will tear the flesh right off.
Good water movement is much harder to attain than people realize. People just assume they have 20x turnover and all is good. But the 20x doesn't help much if half the corals are not getting that turnover. Water movement is probably one of the biggest reasons people have such problems with corals especially when they start to grow. The basic idea is to watch your corals to make sure they are getting good, flow. The actual turnover amount is not as important, but by making sure they have good flow you will hit the 15-20X anyway. With a new tank it is very easy to get good flow throughout the tank as there are very little obstructions, as the coral grow is when you need to periodically get and re-adjust your flow.