Aiming at night time spaceborne imaging, we compare the expected performances of a low-light-level visible sensor
with a conventional IR sensor. The low-light-level visible sensor, an electron multiplier CCD (EMCCD), is a close to
ideal photon counting device, with possibly negligible dark current noise and negligible readout noise. This fact, along
with the significant improvement of diffraction (about an order of magnitude), suggests an interesting competition
between the two technologies. In essence, this is a tradeoff between noise and optical performances (favoring the visible
channel) and basic target radiance (favoring IR). Other factors such as reliability and cost can also play an important role.
While we consider two different spectral ranges with different imaging content, we are able to conduct a cautious
theoretical comparison based on standard targets in various lighting conditions. We show that for a given set of system
parameters, even when lighting conditions are favorable, i.e. a night with a full moon, the low-light-level visible channel
performances are inferior to those of an IR channel. We also comment on the significance of the system working point
regarding performances under varying condition.