OOgle and T71 - if the casualty is injured (the reason you are going to get them in the first place) then you are more likely to injure them further or lose them altogether trying to get them into a dinghy - try doing it in anything more than a 3 -4 foot swell and you will see what I mean.
The hi-line is a tried and tested technique and makes winching to yachts and other small vessels easier not more difficult.
The only way of getting a spinal injury off a yacht at sea would be to let the winchman prep and immobilise the cas and then do a stretcher lift out of the overhead with the boat crew controlling the hi-line to prevent a big swing.