Igor,
I wish that were how it is, because that is the best way to describe the two different things. In a perfect helicopter world, Vortex ring is aerodynamic downwash eating, and settling with power is too much weight or too little engine. Unfortunately, the "official" definitions sort of trap us.
SWP and VRS are the same, according to the FAA:
http://www.geocities.com/flyingmouse1/Chapter_9.html
By the way, I put the VRS web site up on a real server, where it won't shut off:
http://www.s-92heliport.com/vrs.htm
note that even the FAA is confusing the two things, as they warn you to avoid, "hover out of ground effect at altitudes above the hovering ceiling of the helicopter" as if that is VRS.
OH well.
The important thing for ppruners is to make sure they have enough power to perform the hover they intend. If they do, then they can make a vertical descent with relatively low ROD with no worries about VRS, until they get to a ROD of about 50% of their downwash speed.
I have been in a real case of VRS during some Cat A vertical rejected takeoffs, where I was at about 8 knots forward speed, and at 25 fps ROD, when the bottom fell out, and I was suddenly doing 50 fps when passing through 50 feet (that means 1 second to crunch time, sports fans!) I pulled an armfull of collective at about 5 feet, hit the top collective stops at 1 foot, and whacked the ground at 13.6 feet per second (twice the design sink speed) bounced up and (to make sure I had learned my lesson) hit again at 8 feet per second. To its credit, the S-76 was a lot stronger than advertized, otherwise someone else would be writing this. We wrinkled one stringer in the tail cone.
Theoretical VRS should have been about 25 feet per second.