Firebug vs Firefox's native developer tool - Part 2

Other useful information from Firebug are

• Amount of data loaded from cache (this value is not shown if “disk cache/memory cache” is turned off via about:config
• Onload time. 

While some active object (such as chartbeat) would continue to run, "onload" time is the time taken for page to load fully in the first time – the time that the “spinning” icon stopped.