callbacks vs coroutines (vs generators)

Question

I'm creating a web application in python using tornado web server. I'm using Motor for mongo db connection with tornado web server.

i'm referring to tornado motor docs.

in my application i'm uploading data from csv or other data sources and doing some machine learning operations. all the meta data and other required details have to be stored in mongo DB. Web page is a little heavy(as it has a lot of visualizations other operations).

Some examples i tried for learning motor

Example of call back:

import tornado.web, tornado.ioloop
import motor

class NewMessageHandler(tornado.web.RequestHandler):
    def get(self):
        """Show a 'compose message' form."""
        self.write('''
        <form method="post">
            <input type="text" name="msg">
            <input type="submit">
        </form>''')

    # Method exits before the HTTP request completes, thus "asynchronous"
    @tornado.web.asynchronous
    def post(self):
        """Insert a message."""
        msg = self.get_argument('msg')

        # Async insert; callback is executed when insert completes
        self.settings['db'].messages.insert(
            {'msg': msg},
            callback=self._on_response)

    def _on_response(self, result, error):
        if error:
            raise tornado.web.HTTPError(500, error)
        else:
            self.redirect('/')


class MessagesHandler(tornado.web.RequestHandler):
    @tornado.web.asynchronous
    def get(self):
        """Display all messages."""
        self.write('<a href="/compose">Compose a message</a><br>')
        self.write('<ul>')
        db = self.settings['db']
        db.messages.find().sort([('_id', -1)]).each(self._got_message)

    def _got_message(self, message, error):
        if error:
            raise tornado.web.HTTPError(500, error)
        elif message:
            self.write('<li>%s</li>' % message['msg'])
        else:
            # Iteration complete
            self.write('</ul>')
            self.finish()

db = motor.MotorClient().test

application = tornado.web.Application(
    [
        (r'/compose', NewMessageHandler),
        (r'/', MessagesHandler)
    ],
    db=db
)

#print 'Listening on http://localhost:8888'
application.listen(8888)
tornado.ioloop.IOLoop.instance().start()

Example of coroutines:

from tornado import gen
import tornado.web, tornado.ioloop
import motor

class NewMessageHandler(tornado.web.RequestHandler):
    def get(self):
        """Show a 'compose message' form."""
        self.write('''
        <form method="post">
            <input type="text" name="msg">
            <input type="submit">
        </form>''')

    @tornado.web.asynchronous
    @gen.coroutine
    def post(self):
        """Insert a message."""
        msg = self.get_argument('msg')
        db = self.settings['db']

        # insert() returns a Future. Yield the Future to get the result.
        result = yield db.messages.insert({'msg': msg})

        # Success
        self.redirect('/')


class MessagesHandler(tornado.web.RequestHandler):
    @tornado.web.asynchronous
    @gen.coroutine
    def get(self):
        """Display all messages."""
        self.write('<a href="/compose">Compose a message</a><br>')
        self.write('<ul>')
        db = self.settings['db']
        cursor = db.messages.find().sort([('_id', -1)])
        while (yield cursor.fetch_next):
            message = cursor.next_object()
            self.write('<li>%s</li>' % message['msg'])

        # Iteration complete
        self.write('</ul>')
        self.finish()

db = motor.MotorClient().test

application = tornado.web.Application(
    [
        (r'/compose', NewMessageHandler),
        (r'/', MessagesHandler)
    ],
    db=db
)

print 'Listening on http://localhost:8881'
application.listen(8881)
tornado.ioloop.IOLoop.instance().start()

How do i compare the benefits or performance of each example ? Both example do the same functionality. What should i use ? callbacks, co-routines, generators ? I need good performance and flexibility in my application. there are some examples in this link also https://motor.readthedocs.org/en/stable/tutorial.html