We begin at the table. We note where the chairs sit, where the head of the table is, and how the family uses it. A table used for homework in the afternoon and dinner in the evening wants steady daylight with no hard glare. A table pushed against a wall needs light from above, not from the side.
From there we look up. A VELUX window over the table gives direct light from above, which is bright and flat. Slightly off to one side, it gives a softer, more directional light that shows the food and the faces better. Both work, and the choice is personal.
We also consider the room's other light sources. A kitchen-diner with patio doors at one end only needs daylight at the other. A rooflight over the far end balances the room.
Evenings matter as well. A rooflight that gives a bright table by day can show you the night sky and the glass at night, and the glass reflects the room back at you. A blind solves that, and on a table you use after dark, a blind is worth having in the plan from the start.
A table pushed against a wall needs light from above, not from the side.