The differences in boxes are summarised here
You can't add to apps on the 4k box. They are fixed by netgem. Also on the 4k box you get internet exclusive channels not on the hub.
However some of these you can get via free apps such as Pluto on the hub.
Downloading is easy, but you can run out of space if you download too many and despite what it says, adding a micro SD card does not expand the memory for more apps. There is a way using developer mode but when testing this for TalkTalk I bricked 3 boxes, so wouldn't recommend it.
As I mentioned to you previously I prefer to have my own box rather than rent one from TalkTalk and have a BT pro box and a Manhatten one. Both record and have the main apps and I don't have to pay a fee to TalkTalk.
As you will be getting a smart TV you will find this has the main apps and you would really be replicating the TV functionality by having a non recordable box
Plenty to ponder there.
From the 29th of March our TalkTalk Community will move to peer-to-peer support and the TalkTalk team will no longer be here to support with queries. Don’t worry we still have plenty of ways to reach out if you need to speak to TalkTalk directly. For more details check out the link here:
How to contact TalkTalk Broadband - Help & Support.
