The back button should always be faster than the 'home' link because it should retrieve the page as it was, and in the same position from the browser cache. So it doesn't normally query the server at all. At least that's what Firefox does, and I'm pretty sure most browsers do.

Does it do the same in both IE and Chrome? Try clearing the cache - maybe it's corrupt.

Personally I rarely use the back button; I load threads in a new tab, with the middle button, then delete the tab when finished with it, which returns to the main page. But it all depends on your style of browsing.