If easy resale is your main consideration (as you said in the original question), it has to be Dark Silver; it's such a known quantity and it is likely to stay in production for ever, while it's probably fair to assume that Sparkling Silver will be replaced by something else within a year or two (in much the same way as Indi Blue, Hyper Blue, Liquid yellow and Velvet Red came and went).
Personally, as long as the colour isn't going to be a
major obstacle to resale, I wouldn't give resale any further thought and just go for the colour you like

Sparkling Silver is much more unusual and interesting....

May '04 - Feb '07 R50, Feb '07 - May '10 R53. Enjoyed our time with MINI's, but ran out of space! Now Focus RS & Land Rover powered...