The Android boxes are a minefield and everyone I know that has one does so for only one thing and that is to circumvent paying for things, if that is not in your interest I'd say go for the Roku.
In addition the Roku eco-system is pretty much the only one that has Netflix, Amazon and NowTV if you have all 3 of those.
Depends what you want it for I suppose?
Roku is purely a streaming device, you have to stay in its ecosystem and run their approved apps. Plex can be run on Roku but Kodi cant, which makes it a no go for me personally.
Android boxes do everything the Roku can do plus have loads of flexibility to expand it how you want.
Plex is a more plug and play system in my opinion (as its very easy to setup/use) while android boxes are for people who like to tinker and play around a little.
I'd say go for a android box but again its entirely on how you want to use the device.
Would an Android box allow to view UK catchup TV from ITV, 4 and 5 with minimal fuss or would I need to open individual apps for each broadcaster?
Oh it may do, just basing it upon the last time I looked. I only use PLEX, Netflix, Amazon and NowTV.
Would an Android box allow to view UK catchup TV from ITV, 4 and 5 with minimal fuss or would I need to open individual apps for each broadcaster?