When discussing heaven versus moksha we have to realize the inner meaning of heaven and moksha. Heaven (Swarga Hinduism) is a place in core of Sun where souls atmans hibernated whenever necessitated.
After death of human body the released soul atman, consciousness immediately manifests a new body to start a new journey of life. What if matching parents are not available on mother earth? In this situation the soul atman hibernates in heaven or hell. In heaven (swarga) if the residual balance of karma at the time of death is positive and hell (naraka) if negative!
Heaven (swarga) existed in core of Sun where temperatures exceed millions of degrees centigrade. It is in such high temperatures a soul atman felt comfortable. On the contrary hell (naraka) existed in periphery of sun where temperatures were considerably less. It is in such low temperatures a soul atman suffers for eternity.
Sooner matching parents become available on mother earth, the hibernating soul atman in heaven or hell immediately manifests a new body to start a new cycle of life on mother earth.
Comparatively indulging in spirituality when human beings finally succeed reaching state of enlightenment followed by moksha salvation, the soul atman within finally liberates from cycle of birth and death forever. The cosmic journey for soul atman finally ends. This liberated soul atman finally merges with God enters kingdom of God, Vaikuntha in Hinduism.
Reaching moksha is the ultimate goal of life on mother earth whereas heaven carried no spiritual meaning. If the religious clergy or pundits assure a seat in heaven, it is primarily due to their commercial inclinations having nothing to do with religion or spirituality.