I can understand that with the RUTX11, having both 2.4 and 5 GHz networks, you make use of separate radio's and then throughput will be better. Although you wil probably still make use use of the same antenna's which might impact throughput. Furthermore, the RUTX11 is not very cheap especially compared with e.g. the RUT240, new RUT360 or Alfa Networks.
I need the WiFi to be able to work mobile from my camper and are therefore searching for a good solution with highest possible throughput.