Well my first turbine was a 500C then purchased a 206B3, sold the jetbanger 12 months later for a 500D, since then have owned 4 x 500E's, but have always kept the D.
That probably sums up which one I would go for. Most important about either machine, make sure you have it surveyed by someone who knows the type before buying. Then have a descent maintenance company look after it.
As for resale value, the 500 wins everytime, never sold one for less than I paid for it. Have a look and see how many 500 are ever for sale compared to 206's