Is worshiping at home more important to a Hindu than worshiping in Mandirs?

no they are both equally important

1. The temple is specifically designed to increase belief in god and maintained by professional priests. Every one who visits it come to increase his belief in god.

In contrast, home is a multipurpose space and the atmosphere is not ideal for worship.

2. Hindus believe in god and don't accept it as a fact. This is because if god fails in solving their problem they can solve it manually. Worshiping at home reduces belief and thus dependence on god.

3. God is more powerful when in the real world than when within us. Worship in Temple ensures us that our god is in the real world and not within us.

4. God is more effective when all our activities are interlinked and is ineffective if they are delinked. It is for this reason that in temples more attention is paid by priests to Brahmin worshipers. The intention is not to degrade non Brahmins but to make every one to use Brahmana Varna and link as many activities as possible and not pray for some specific reward.