Thanks for your comments guys.
I agree that the S4rs is worth the extra over the S4r IF you are paying full price for the S4r.
But as the S4r has been out longer, there are more deals available. Pegusus have a pre-reg 55 plate S4r for £6,789, which makes it nearly £3k cheaper than the S4rs.
Really torn on this one. Half of me saying sod it, you only live once and the other half thinking about having the extra £3k.