These two parameters provide ways of balancing audio quality vs. conservation of computer power.
When this is activated, the loop file playback is calculated using a more advanced interpolation algorithm. This results in better audio quality, especially for loops with a lot of high frequency content.
High Quality Interpolation uses more computer power - if you don't need it, it's a good idea to turn it off!
Listen to the loop in a context and determine whether you think this setting makes any difference.