What is the difference between the SAS-TEC and Soft pads?

The SAS-TEC pads are based on a shock absorbing foam technology, which hardens in case of impact, so if you require protection from immediate impacts, you should go with these.

But if you require knee protection due to a high frequency of kneeling with a heavy rucksack, then you should go with the SOFT pads, that are made from foam that provides extra cushioning.