ResponsePromise vs. regular promises

gistfile1.js

function onerror(err) {
    // do stuff
}

///////////////// Piping /////////////////

// ResponsePromise
fetch("./contacts.csv").catch(onerror).body.pipe(new CSVParser());

// Regular promise
fetch("./contacts.csv").then(function(response) { response.body.pipe(new CSVParser()); }, onerror);

// Regular promise with getter + invoker
fetch("./contacts.csv").catch(onerror).get("body").invoke("pipe", new CSVParser());

///////////////// Streaming video /////////////////

// ResponsePromise
var video = document.createElement("video");
document.body.appendChild(video);
video.src = fetch("./fr.ogg").body; // How do we handle errors here?

// Regular promise
var video = document.createElement("video");
document.body.appendChild(video); // Is it OK to append a video before setting src?
fetch("./fr.ogg").then(function(response) { video.src = response.body; }, onerror);
// or, if video.src would accept Promise<Response>:
video.src = fetch("./fr.ogg").catch(onerror);

// Regular promise with getter
var video = document.createElement("video");
document.body.appendChild(video);
fetch("./fr.ogg").get("body").then(function(body) { video.src = body; }, onerror);
// or, if video.src would accept promises:
video.src = fetch("./fr.ogg").catch(onerror).get("body");

///////////////// Headers /////////////////

// ResponsePromise
fetch("./contacts.csv").then(function(response) { console.log(response.contentType); }, onerror);

// Regular promise
fetch("./contacts.csv").then(function(response) { console.log(response.contentType); }, onerror);

// Regular promise with getter
fetch("./contacts.csv").get("contentType").then(console.log.bind(console), onerror);