I would take the RB over the S1 if they are priced around the same but if you are getting a good price on the S1 then take it and put the shaft from your RB 5 port into it.
I think 3-port Turbos are legal under Roar rules also. If so then put the Turbo button from the RB onto it also. Might as well get all the advantage you can from the legal parts of the 5-port as it will as good as give you a interim S3
