Are you looking for roost protection or impact protection?
Basically a Thor Sentinel will do nothing for impact protection while the EVS and 661 models you were talking of would help during a fall. I'm not saying you'll be bulletproof while wearing them, but they will do a better job of protecting your shoulders and arms.
I say this becuase I was recently injured while wearing a Thor Sentinel which I have now sold. I bought it thinking I needed roost protection and good looks, as inexperience made me a "girly-man". After fracturing my humerous up near my shoulder (at the rotator cuff), I realized if I'd had something to protect my outer shoulder, I may have got through the accident with just some bruises and scrapes. As it was I had serious "dirt rash" on my arms and as stated above, a fractured upper arm bone. This injury has been extremely frustrating and recovery is supposed to take up to six months, possibly more. I haven't been able to ride since July, but I'm coping, becuase had I not been injured, I would be in Iraq now anyway.
What I'm getting at, is that roost hurts, but crashing hurts worse and can lead to injury. You should concentrate on finding a product that will provide all-around protection (through padding) more against the impacts of falling rather than rocks hitting you (which only hurts if you're a girly-man, haha).
Hope this helps. Good luck!