First of all that's the last gen R&S HMO, although very similar to the RTC.
I watched both videos and the R&S looks superior to me in build quality. And Dave's reaction to several aspects of the build quality of the R&S was very favourable. Drooling over almost every aspect. Then when we come to the software the R&S runs silky smooth. And with a boot up time 3x faster. The rotary knobs are much more sturdy, BNC connectors are gold plated and beefier, expensive high quality molex microfit connectors used exclusively for all internal connections. Power supply caps superior. Silent fan on the R&S, compared to a noisy one which Dave commented sounded horrible. Regarding the PCB itself, you can tell the Siglent is Chinese. Where the ultra clean board on the R&S is German designed, and built in house on the SOTA machines at R&S's own European factory. And based on the standard of excellence of all of the clearly visible components, I think it's safe to assume R&S also used superior MLCC's, resistors, diodes, inductors, and polymer caps on the PCB.
Watching this video the knobs appear to be very sloppy as well. And the GUI just seems clunky and unrefined compared to the R&S. Well known software glitches aside.
Sorry guys not sold on the build quality.