When should one use BytesIO .getvalue() instead of .getbuffer()?

Question

According to the BytesIO docs:

getbuffer()

Return a readable and writable view over the contents of the buffer without copying them. Also, mutating the view will transparently update the contents of the buffer:

getvalue()

Return bytes containing the entire contents of the buffer.

So it seems as if getbuffer is more complicated. But if you don't need a writable view? Would you then simply use getvalue? What are the trade-offs?

Minimal Example

In this example, it seems as if they do exactly the same:

# Create an example
from io import BytesIO
bytesio_object = BytesIO(b"Hello World!")

# Write the stuff
with open("output.txt", "wb") as f:
    f.write(bytesio_object.getbuffer())

Answer 1

Using getbuffer() is better, because, if you have really BIG data, copying them may take a long time. And (from PEP 20):

Explicit is better than implicit.

But value is undefined - it may be str or bytes. Buffer is always bytes.