Interesting that you seperate them as if they are not both pillars and foundations of the truth.
I know the scripture reference is that the church (local and visible) is the pillar and foundation of the truth. The local congregation/assembly of saved baptised believers.. covenanted together to carry out the Great Commission and Commandment.
But the bible could also be called the 'pillar and foundation of the truth'.. ..
That would not be a false statement. I just don know of a direct scripture that says this.
I would say the choice is not either/or here.. but that both the bible and the church are the pillar and foundation of the truth..
It's just that 'the church' is the direct reference from scripture