“This official power supply may not be the cheapest supply out there but for a Pi3, I wouldn't use anything else.
Other (cheaper) power supplies have caused me issues with fluctuating power. I have bought several of these and they are as solid as you would expect.”
“I've tried many unofficial 2-2.5 Amp chinese power supply, many of them couldn't supply enough power for the pi3 at 100% CPU use (without any periferials).
This one works like a charm, there is no power shortage. Recommended!”
“I used a 2a quickcharge adapter before, but my pi had some issues running at full speed with my retro pi installation. The 2.5a official power supply fixed that issue for me!”