In my experience, surface roughness can vary quite a bit between SLS and MJF processes. SLS tends to produce a slightly rougher surface compared to MJF due to the nature of the laser sintering process and the powder bed fusion technique. But both methods can achieve relatively smooth surfaces with proper parameter optimization and post-processing techniques like sanding or polishing.

We conducted experiments in-house with SLS and MJF 3D prints and we actually have some concrete data to share. We measured the surface roughness of SLS prints with different surface finishes: PA12 raw part (approximately 8 µm), PA12 bead blasted (4.5 µm) vs PA12 vapour polished + dyed black (2.5 µm). And we did the same for MJF prints and 5 other 3D printing technologies. I would recommend you to check our article on this topic: https://xometry.pro/en-eu/articles/3d-printing-surface-roughness/