As we mentioned in the last answer, búdà不大 means ‘not very’, while dàbù大不 represents a strong negative tone. For example,
Nǐmende guāndiǎn dàbù yíyàng
Your opinion significantly not same
‘Your opinions are very different.’
However, dàbù大不 can only match a limited number of words such as yíyàng 一样 ‘same’, xiāngtóng 相同 ‘same’.