HDD GURU FORUMS

In terms of speed which one would be more faster?

I heard USB 3.0 is insanely faster than usb 2.0, so I am wondering if it would perform faster than a 5400 rpm laptop hdd?

What I really mean by is, boot from internal HDD (which I don't really want to) or boot from external usb 3.0 HDD?

I much prefer to use a external HDD, but I am just wondering if it's worth "speed" wise?