I’ve swapped from using the 661 KS to the (older style) POC pads.
I only really use them when riding DH and had previously used the 661’s for years. They were always ‘alright’, I found they always bunched up & annoyed me after a while. Plus if you washed them a lot something seemed to happen to the material & would end up rubbing your knees raw (everyone who I ride with who used them had this issue).
The POC’s are a lower profile, and like for like sizing (medium) seem to fit better. So far they don’t bunch up, despite only having one velcro strap.
I found some on offer at the same price as the 661’s, so thought I would try them, I don’t think I would pay full retail for them, as they are bloody expensive!