I have a query here. Does the 'Fetch' Feature actually works? Which is present in the different webmasters tools. I own a couple of blogs. In some of them I fetch manually and some of them I do not. But all works at the same speed. I have almost the same quality backlinks to them.
Well, it depends on several factors and not at all just backlinks that how frequently google or bing will crawl your site. Site popularity, site age, social media share are also countable factors. Have you tried fetching the sites which you are not doing now and not fetching the sites which you are fetching now?
Fetch is typically set on a timed basis, while Push happens in real time. Fetch will use up your battery faster, as it requires your device to check the email server, while Push only needs to let the email server know where to send the notifications. If battery power is an issue, try to enable Push on your iOS device, if available.