I just got the XBR. Haven't run it yet, but I compared its size to the old Super Sport Plus. It's about just as big (but longer, narrower), and with a slightly narrower footprint.
New features (compared to the SS+): LiPo LVC, autodetect brushed mode, can run the motor in reverse direction (without rewiring), fan power output pins (shared with the 1.5A BEC, so dont get carried away).
Old features it's missing: no more 3A BEC, no more Sportsman mode.