I'd say that's the issue. The 3165 is AC, but only has a max speed of 433 Mbps (this is theoretical speed) you'll never get anywhere close to that half that speed is pretty good. Your Samsung has a Murata KM5D18098 wireless module, this is also AC and I think it's MU-MIMO 2 x 2. So it actually has dual antennas so the speed is probably around 800mbps (again theoretical) so again half that is reasonable. Wireless is also a lot like a hub in the sense it has to detect and handle collisions when more than 1 device is talking so that can affect speed. Plus you have attenuation, distortion, refraction, absorption, diffraction, interference affecting the signal