Sensitivity of a particular instrument depends on the analyte and its matrix, the method of separation, the method of ionization and the mass spectrometer. Disregarding everything except the mass spectrometer analyzer and having worked in a laboratory with quads, ion traps, and time of flight instruments, the ion trap gives the highest ion counts for the same sample and hence the most sensitivity. This seems to be do to an ions residence time in the vacuum system before it is detected or measured. The ion trap is the most compact device and  there seems to be less chance to quench the ions in the vacuum chamber before they reach the detector.    

very interesting indeed. Thanks!

It's hard to answer that out of context.  Sensitivity (just as a specification) varies widely from analyzer to analyzer and between manufacturers and models.  For a practical answer, you need to consider the specific problem to be solved.  For target compound identification, triple quadruple MS can give very low detection limits because selected reaction monitoring discriminates well against chemical background.  For non-targeted analysis, time-of-flight does very well because you can detect all of the components in the spectrum under high resolution conditions with full sensitivity.  Ion traps have their own advantages and disadvantages for specific problems and this does not even take FTICR and Orbitraps into account.  Sensitivity also depends strongly on the ionization method.  The lowest detection limits of all are probably for electron capture negative-ion analysis.

This could help https://www.researchgate.net/publication/257839031_Comparison_of_the_sensitivity_of_mass_spectrometry_atmospheric_pressure_ionization_techniques_in_the_analysis_of_porphyrinoids?ev=srch_pub

Article Comparison of the sensitivity of mass spectrometry atmospher...

Hi, I agree it mus be clearly explained approach-based as mentioned above, depending on which kind of study you are performing, and not related to the intrinsic characteristics of the analyzer.

When using an analyte discovery approach (not dedicated to a few well defined analytes) the sensitivity depends a lot on the background (avoid traps) and cycle time (avoid quadrupoles), so TOF and Orbitrap, that u dont mention, is no doubt the most recommendable.

When studying specific analytes the way to go is applying targeted approaches, based on tandem MS; background is not any more a bottle neck and triple quadrupole (with quick performance now that is not scanning in discovery mode) and trap (because of its ability to accumulate ions as much as needed) become ideal choices, while TOF and orbitrap cannot be ideally applied in this sense.