For HCAD appraisal, is there any point to contesting the market value (not the appraised value)?

This may be a dumb question, but does the market value actually matter as long as you have the homestead exemption? i.e. If I think my home value actually went up 10% this year, does it matter that HCAD thinks the market value went up 25%? Is there a reason to contest the market value assessment?