README shows two ways to use different kernel

The README says:

> If you wish to use a specific Jupyter kernel, you may pass the kernel option. This enables you to use ob-ipython with languages other than Python. You need to have the Jupyter kernel installed and working before you can use this.

> When mixing code from different languages you will need to make use of the session argument.

> #+BEGIN_SRC ipython :session :kernel clojure
> (+ 1 2)
> #+END_SRC

But then right below that also says:

> If you have other kernels installed, you should be able to evaluate blocks by providing jupyter-X as the language, where X is the language name recognised by jupyter. For example, you can do something like this:

> #+BEGIN_SRC jupyter-R :results raw drawer
> x <- 3
> x
> #+END_SRC

Which of these methods is the preferred way to use a non-python kernel?