bios default is normal setting in terms of speed, high performance is faster, but the reason it is faster is it will not only make your system start with high setting (sometimes it won't work due to the other parts on your system, for example RAM) and it will also neglect some of the tests it will run on normal setting (like memory test)
try to run it in high perform to see if your system able to run it, then it really depends on your taste if you want the system to run those test every time it boot