Based on their locations on the periodic table, which best compares the properties of the metalloids arsenic (as) and antimony (sb)?

antimony has more metallic character than arsenic.

Justification:

1) Both arsenic (As) and antimony (Sb) are in the same group, 15, of the periodic table (they both have 5 valence electrons).

2) There is a clear trend in the periodic table about the metallic character in a group: metallic character increases down the group.

The reason of this is that the ionization energies decrease as the electrons are further away from the nucleus (due to the shielding effect of more electrons in between the nucleus and the valence electrons).

3) Since antimomy is in the period (row) 5 and arsenic is in the period 4, you can conclude that antimony (being below arsenic) has more metallic character than arsenic.