Well, there's one thing going for pull over push - and generally I am strongly in favour of push.
With push, you need to know where to send the data. So you depend on a fixed configuration. With pull, you can essentially do a periodic nmap sweep to discover and update the monitoring data sources.
Another nice thing about pull is you only pull from the authoritative source. If you have a daemon that has gone rogue your load balancer or naming system can throw it out of the named group/job/whatever even if it can’t shut it off. With push you might have zombies pushing duplicate data for what should be a unique target.
With push, you need to know where to send the data. So you depend on a fixed configuration. With pull, you can essentially do a periodic nmap sweep to discover and update the monitoring data sources.
That's one less thing to go wrong.