Personally I love moonstone, I have seen an F10 M5 in that colour and it looked
absolutely stunning. Would have been my choice but then decided on red as it was cheaper and I was in a 'fun' mood on the day I spec'd the car
I'd say moonstone is a lot 'softer' than silver and far more interesting as it has real depth to it... but colour is so much down to personal choice and what floats yer boat.
I've had two silver cars before, unfortunately the second got smacked up the rear and it took the dealer's official bodyshop over 9 months to get the colour right; they eventually decided to respray the entire car. Silver looks OK new, but I see so many silver cars these days that have an 'odd' panel, it's put me off