Boot Times & Run Times

I've seen it stated on various forums how much faster a system will be once installed to a hard drive, rather than running in live mode from a USB stick. In fact I've even seen figures of 10x and 15x faster quoted. Sorry but I haven't yet seen any evidence to support this. I've tried a vast number of different distros over the last couple of years or so, and I haven't yet come across one that has been significantly quicker once installed. Please note I said "significantly". Ok, so there's been one or two...