Is the macbook retina's soldered RAM in any way faster than typical RAM? You would think it would make some kind of difference...
Not really. Access times might be faster by a handful of picoseconds, since the electrical impulses would travel a slightly shorter distance by taking away the circuitry in the socket. However that distance is dwarfed by the variance in placement of the RAM on the logic board — sometimes it's closer to the CPU, sometimes farther away.

The predominant factors for speed of RAM are the clock speed and bit width, not the physical layout.