Answer is: more ionic.
When the electronegativity difference is greater than 2.0, the bond is considered ionic. 
Electronegativity (χ) is a property that describes the tendency of an atom to attract a shared pair of electrons. 
Atoms with higher electronegativity attracts more electrons towards it, electrons are closer to that atom. 
For example fluorine has electronegativity approximately χ = 4 and sodium χ = 1, fluorine attracts electron and it has negative charge and sodium has positive charge.