The RS4S has all the same gauges, the same HICAS, the same bigger stronger driveshaft, the same bigger anti roll bars.
What it doesn't have is an FMIC, multi throttle bodies/front facing plenum or twin turbos, although it does have VCT.
If you add up the cost of bolting on the missing bits, the ease of changing turbos then the RS4S should bring you out ahead financially for similar performance. There is nothing magical about either engine when it comes to making power, with decent parts and good tuning they will both make enough power for a streetable car but I would strongly suggest not oversizing the turbo/s to get a big headline power figure as it will hurt the drivability down low. These things are pretty heavy and you need all the help you can get like VCT etc to make power where you can use it. Ultimately you should buy whatever makes you happy because both are pretty good things.