It's swings and roundabouts;
The premium of buying from VW get's you a one year warranty and (they where doing a 30 day 'lemon' return), it depends if you think it's worth it.
Private sales, come sold as seen but generally cheaper.
As always buy on condition regardless of the source. I found a red 2006 model from a private seller (18's, lux pack, cruise, rcd500, armrest, mfsw, 7500miles)
for £12,000, expensive but it was basically new!