The former is cited as a "little bit of an overhaul" with no cosmetic changes to the game experience itself. Jagex does, however, claim that the popular minigame has had a lot of work done under the hood. According to the update notes from Runescape content developer Mod Nancy,
On entering the Duel Tournament waiting room, you will now be assigned to a single registrar. This assignment is partially based on combat level, but also on many other factors. The registrar you are assigned has a Tournament Rank cap. You will not be able to gain rank beyond that cap until you move on to the next registrar. The best way to move up a registrar is to train your combat skills.
Registrar caps are as follows:
Registrar 1: rank cap of 1999
Registrar 2: rank cap of 2499