All-soldered RAM isn't faster.

No. Dual-channel depends on having two memory channels active, not on whether the chips are soldered or socketed.

A laptop with two soldered RAM chips runs dual-channel just fine. A laptop with one soldered chip and one SODIMM slot can also run dual-channel — as long as they match in size, speed, timings, and ideally rank. Manufacturers make it work.

Any performance delta between the two setups is tiny. We’re talking single-digit percentage differences in synthetic benchmarks, often zero in real-world use. The “performance benefit” of all-soldered RAM is a myth.

The real trade-off is flexibility.