The extra padding on the Sam Hill pads seems worthless, and there is a gap in between the main pad and extra padding. The SAS Tech pad is very stiff, then they put the opening to remove the pad right for laundering right at the knee so it abrades your knee cap. I don't get the positive reviews...
I've had my Sam Hill knee pads for 2 years now, and I wear them on ever ride. So they get a fair bit of use. That said, I definitely haven't tried all the pads out there. I just have been pretty happy with them, especially since they are a higher rated pad (certification, not like, review rating or something) than many "trail" pads.
The SAS tech pad is pretty stiff when cold, but seems pretty pliable when its warmed up. On my knee they don't contact my kneecap (or at least don't abrade the knee/or at least don't notice it). If I haven't washed them recently, and I've been sweating a lot, they do make me itch/leave a little red mark on the knee above/around the knee cap on longer days, but when I wash them that goes away.
The padding around the main SAS stuff isn't connected, so it is possible to get hit between the foam, and the main pad. That said, I say possible, because I've never taken an impact between them, as the gap is pretty small. They have however taken their fair share of frame/stem/pedal type impacts, and definitely helped with some other trail type impacts. I like the extra padding enough I wouldn't wear a knee pad without extra padding around the sides (at least for an aggressive trail type pad).
The other thing I'd struggle to give up, is the really long upper and lower parts of the Sam Hill pad. The upper part lets me tuck the pad under my chamois, and its never moved, at all. Plus the extra length on the bottom from the foam is really nice, and has prevented a bunch of pedal to the shin moments. My buddy has some Leatt Airflex Pro knee pads, and those have noticeably less coverage. That said, they do have more ventilation.