If the pertinent specs for the specific A/D chip used in the SDS scanners have been published, I haven't seen it.The receiver chip in SDS100 and RTL-SDR are more or less of the same performance.
However a ham friend (with decades of two way radio experience professionally) has said that the SDS performance is a disaster on VHF in his area, a metro area.
I have heard that the SDS is designed to block-downconvert the desired frequency band into the low-HF range, say 5 MHz, and the entire resulting I.F. swath which is a few MHz wide, is digitized. If we assume Ubbe is correct and the SDS uses the same 8-bit ADC as the RTL-SDR, and we use the rule of thumb that each A/D bit is equivalent to approx. 6 dB of dynamic range, this would place the SDS in the 48 dB DR ballpark (quite a poor spec. value -- especially considering this ranges over a few MHz, not just immediately adjacent to the signal center frequency).
This would also be a good match with the variation in reports, i.e., good for some users and not-good for others. Reception on a given frequency can be affected by other signals that might be as much as a few MHz offset from the desired frequency.
Ah, but these SDS filters do absolutely nothing for in-band interference.That's ridiculous. The SDS has front end filters the SDR sticks do not.