My understanding is that it comes with Hill hold but not (Hill) Hold Assist (code UH2). Which one did you mean? The "Assist" bit means (when turned on) that when the car comes to a complete stop, the car holds the brakes on for any length of time, until you touch the throttle, then it relases: and it also puts on the hand brake for you when you park.
Re the price comparison R or S3: remember it isn't apples with apples, so maybe the extra isn't as bad as it first appears. For example the S3 has Nappa leather standard, as opposed to the R's std cloth or if you add the additional cost for R leather it's still not comparable to the S3's Nappa. Also thing like the S3's pop up display is a step above the R's etc. However some things work the other way - you have to pay extra to get a rear arm rest etc. For me the biggest differences were 1) the lack of refinement I found in the R, compared to the S3; and that's important to me and 2) the options that I wanted - I could get on the S3 but not on the R (e.g. B&O sound etc).
Anyway, good luck deciding ....