Mind's Eye If we go purely by card-drawing efficiency, Mind's Eye is one of the greatest artifacts for Commander, letting you draw at the very least three extra cards per turn as long as you have available mana
It also supports aggressive decks (based on dealing damage with creatures) which, in general, have a very high difficulty in Commander compared to other formats, due to the much higher amount of life points, and there are usually three other players to deal damage to
In our Bear Tribal, since it counts as a Bear, on ETB it triggers Ayula, Queen Among Bears, so it is a potential removal too (and with good stats for its cmc)
Fewer surprise price spikes, more predictable secondary-market behaviour, and a card pool designed to be reprinted indefinitely