Iirc, DNII and DTII have a twice the power of DN/DT OG, like there is a second chip, not exactly the same, but there is still some code in common.
Whereas the TV is a whole new architecture (running an embedded Linux maybe), with a lot more power, but needing the whole code to be rewritten.
Edit: I have little knowledge/memory of what I am talking about, so take it with the appropriate amount of doubt.
Thx @Bignill bellow for having looked for @dzyndzel 's exact information: