The code understanding question

[engor]

Hi. Is there any profit of using

stream = response.asStream().listen(null);
stream?.onData((http.StreamedResponse r) async {
        int fileSize = int.tryParse(r.headers['content-length'] ?? '-1') ?? -1;
        reader = ChunkedStreamReader(r.stream);

instead of

int fileSize = response.contentLength ?? -1;
reader = ChunkedStreamReader(response.stream);

?

It seems the second case give us the same speed but is little cleaner.