The following sentence is from a text about a new genetic testing method which reveals whether a tumor is cancerous or not, without having to apply chemotherapy. BBC - Genetic testing spared baby unncessary chemotherapy
"We would not have been able to pick this up by any other test - genetic or otherwise," says Dr Behjati.
In this sentence, the structure "....would not have been able to pick..." is too wordy. And it seems that it is used to create a meaning which can also be created by another but shorter structure in the English language: "...could not have picked .....".
"We couldn't have picked this up by any other test - genetic or otherwise," says Dr Behjati.
So, as a non-native speaker, both sentences seem to have the same meaning to me. Do they to you, native speakers?