Which is a more favorable reaction: an endothermic or an exothermic reaction?
Just to retire this question....
The factor that influences the spontaneity of chemical change is NOT enthalpy, but entropy....the statistical probability for disorder. There are in fact examples of SPONTANEOUS ENDOTHERMIC CHANGE in which ENTROPY is increased in the endothermic reaction, and thus the reaction becomes thermodynamically favourable.
A priori, however, the exothermic change should be MORE favourable....but further details of the reaction are necessary....