Which substance has the higher oxidation strength?
Look right here ... .

http://hyperphysics.phy-astr.gsu.edu/hbase/tables/electpot.html

Hypochlorite ion (+0.90 V) has a lower reduction potential in basic solution than elemental chlorine (+1.36 V), so the hypochlorite ion is less strongly oxidizing and more stable in basic solution (which is what you write the reaction for).

Household "chlorine" bleach, which really uses hypochlorite, is made alkaline as one way to stabilize the hypochlorite ion and prevent evolution of chlorine gas.