Originally Posted by SunTzu
I have RT-AC66U (a little better than N66U). Still same performance as DIR-655, why?.
A realistic answer: for two WiFi routers in the same 802.11 mode (b/g/n), communicating with the same client hardware, same locations, most all will have very close to the same performance - because the transmitter power and receiver sensitivity is so nearly identical. The laws of physics
overwhelmingly govern the data rates (ratio of signal to noise+interference, or SINR), and the transmitter amplifier for OFDM (11g/n) requires the 6dB+ headroom - this is due to the 802.11/OFDM specs. Things like noise-power-bandwidth product, adjacent channel interference (since WiFi cannot use channel-wide (20 or 40MHz) filters; by "channel", I mean the next non-overlapping channel. And so on. This is good, because we all benefit from the standards and interoperable products.
The laws of economics preclude a low noise amplifier and a transmitting amplifier for routers that compete price-wise and pay for retail shelf-space these days.
There are a relatively small number of WiFi chip vendors- maybe 6 or so. These appear in dozens of products.
This also assumes the client device is in the same mode: b/g/n and same MIMO arrangement. A MIMO WiFi router/access point doesn't benefit a client device with none, or lesser.
Antenna gain differences can affect things a slight amount (omni-directional antennas). But 2, 6, 9 dB of increased gain is small compared to the path loss in a typical setting: 80dB or more. Many routers have internal non-changeable antennas, for reasons of cost and/or due to MIMO arrangements.
Given the above... the products in a price range and shelf-location compete on management features, ease-of-use firmware, and layer 3 (non-hardware-related) features like QoS management.