Slit vs slitless spectrograph... a large question!
Slitless -> (positive) low cost, simplifed acquisition procedure, not very intrusive (similar to a filter) - (negative) more difficult to remove bakgroung (presence of the galaxy in the backgroud), low resolution, noise from the sky pollution (for me), less precise wavelenth calibration (but the need is lower), less stable specral shape (dependant of focus and seeing for example).
Slit -> (positive) high rejection of galaxy and sky pollution light (very critical for me because I observe in urban condition and also during full moon period), stable line shape and wavelhength calibration, high resolution, more easy to calibrate - (negative) some lost at the slit level (but not very critical if you use a moderated sized telescope - one of the explanation of the use a small telescope like FSQ refractor for me), cost (but relatively moderate for the Alpy), not alway intuitive during the first contacts.
Here the difference between a 1x1 bin acquisition and a 3x3 bin acquisition (the camera is the same, an Aik460 model) :
Note the short exposure time for the 3x3 mode (5 time shorter and nearly same Signal to Noise Ratio). But in 3x3 bin secrum is very undesampled (horrific relative to Shannon theorem), and
consequently some artifact appear (critical for me). The1x1 spectrum mode is more robust to fixed noise. The 1x1 bin improve slighty spectral resolution, relative to 2x2 bin, and of course reltive to in 3x3.
Christian