Selected answers from the Dumb SEO Questions G+ community.
Michael Martinez: It depends (typical SEO answer, I know). What kind of performance do you want to clock? The page speed tools, for example, are all slightly different. Some are better at simulating actual user devices. Some are more aligned with what the crawlers are looking for. You won`t find any "perfect" tool that nails it for every possible scenario. I recommend you try several. And there is a Google tool many people don`t yet seem to be aware of. You should give it a whirl. https://testmysite.withgoogle.com/intl/en-gb
Ryan Logan: Hey Jérome Dingeldein. I wrote a short article on this. You can skip down to the Performance Testing section.
Alan Bleiweiss: I`ve relied on WebPageTest .org for years. GTMetrix is my second go-to.
Fact: Google`s own tool at TestMySite.WithGoogle .com and ThinkWithGoogle .com BOTH use WebPageTest .org as the back end testing system.