The S3 is an awesome bike, very very fun to ride with more than enough power. However I have no doubt at all that the 675 is quite a bit faster than it. They both feel about as fast as each other, but the unfared bikes feel like you're doing 150 when you're at 70. Step off your bonnie and onto the S3 and you'll be amazed at how well it handles and how much power it has, step off the S3 and onto a 675 and you'll be amazed at how powerful it is and how much better it handles.
If you want to have fun at low speeds I'd go with an S3, if you are more likely to do a bit of sporty riding or wet weather riding, go with the 675.
I've gone with a 675 because I love the revs and as incredible as the 1050 triple is I kept running out of revs
