Because of this confusion in terms ( SWP / VRS ) Transport Canada requires that an ACP ask this specific question during a PPC. The FAA really makes no distinction and as mentioned uses the 2 terms interchangeably when in fact they are as different as chalk and cheese.
VRS requires 3 things to come together. A relatively high rate of decent ( most modern helicopters this is at least 500ft/min). Partial power, and airspeed less than translation. Gross weight is not a factor and actually it is easier to get into VRS at a low GW.
SWP or PS as it is also called is simply a condition which requires more power than is available for the conditions. Think loading your 206 to gross at sea level and then trying to land on a mountain at 10,000 ft on a warm day.