Apart from the amount of onboard storage, the remote and the extra maps, you've just described the 720 and the 520 too. They both have all that stuff and the remote is available as an option. The 920's party piece is a motion sensor that can keep an idea of where you are even if the satellite signal is lost.

Also, the 920 replaces the 910; there are 'T' versions of the other two as well..

............the recommended route going round the north side of Trafagar Square - that hasn't been possible for 2 years or so!