Installing R statistics system on 16.04 LTS from Ubuntu repo or CRAN repo?

I have been reading up about how to install the R statistics system on Ubuntu (16.04 LTS).

R is in the Ubuntu repositories (as are many CRAN packages), but quite a lot of documentation and answers seem to recommend installing from the CRAN repos instead?

I realise that the versions in the Ubuntu repo are likely to be somewhat older, but does it contain most/all of the additional CRAN R packages, and I would only really need to use the CRAN repo if there is genuine need for newer packages, or should I just add the CRAN repo to our system anyway?

(My instinct is always to try to minimise variations from the standard Ubuntu packages wherever possible, but I suppose this is rather more of a concern in practice when installing individual third-party .deb packages than adding a (hopefully) well-organised and managed repo?)