Monolog is my logger of choise, but as far as I can tell, the Zend\Log component is just as good. I would have loved to have an interchangable situation, but that is not going to happen anytime soon.
This is an example of the Zend\Log:
$logger = new \Zend\Log\Logger;
$writer = new \Zend\Log\Writer\Stream('/home/robert/example.log');
$logger->warn($'A warning message');
$logger->log($logger::WARN, 'Another warning message');
This is an example of the Monolog: