I'm all for a dark colour (as they are the most rewarding to clean/polish/wax), but that said, I never felt disheartened with Daytona in the same way I did with my Silver A4.
Go with your gut, Manhattan is likely to be the rarer colour as Daytona has been available on damn-near the entire range for the best part of 10 years now!
My girlfriend was 100% sold on Manhattan when she saw it and there was a Daytona A3 right next to it

Deciding whether to get the Tech Pack and Virtual Cockpit is also proving to be a difficult decision
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Any idea when you'll be getting your S3 Saloon?