Why do subscriptions and pages load much faster on firefox?

In my local development app, my subscriptions and loads nearly instantly on firefox with over 300 docs, in chrome it takes 1-2 seconds, in safari sometimes 3-4 seconds, what is causing this?

also i checked the subscriptions in safari using msavin:mongol and it is using “polling every 3 sec” instead of “observing” in chrome, what is causing a local site to be using polling method?