Light BSs have between about 600k and 700k armour, the 7 mil unit powerplant, and fast turning (for Battleships), Light BSs include the Osiris, Mako and Zephyr.
Medium BSs have around 800k armour, the 8 mil powerplant, and medium turning (not as fast as Light BSs, but not as slow as heavies), Med BSs include the Liberty Dread, Bretonian BS and Sarissa.
Heavy BSs have 1 mil or more armour, the 9 mil powerplant, and slow turning, Heavy BSs include the Legate, Kusari BS and Rheinland BS, and everything in-between.
Also, the Liberty Dread and Siege Cruiser are both really rather good ships, and more than capable of tearing through their Rheinland counterparts, especially in fleet combat. The LABC and Carrier on the other hand are awful.
However, as this thread is about the model, all I'd say is remove those fins at the bottom, they may not stick out much, and they are not that big, but Rheinland ships don't have little fins (especially not Rheinland caps), and they look rather out of place. Other than that, it's looking rather nice, though I have noticed some curved faces, which are pretty much non-existent on Rheinland caps, so maybe a slight touch of extra angularity wouldn't go amiss in places such as the mid-section and the plates surrounding the engine.