If I was FORCED to get rid of one (it would have to be a pretty darn strong force

) I'd pick the Dayton (i.e. keep the S3).
Definitely more fun for commuting, hands down win for anything greater than 50 mile trips, and surprisingly capable/nimble in the twisties.
I've found I ride the S3 more now, until I feel "guilty" and take the D675 for a spin.
If you enjoy track days, I'd definitely recommend you get one, though. Great pair

If you just commute with occasional canyon days (not long) then, unless money is not an issue, the S3 will do just fine by itself.