Value of Japan Rail Pass?

I am travelling from Osaka to Hiroshima to Kyoto [day trip to Nara] back to Osaka in one week. Do you recommend that I purchase a JR Pass or will buying individual train fares better value?

You are probably better off buying the Kansai-Hiroshima Area Pass. It is valid for 5 days, so if you finish all your long-distance trips first (Osaka-Hiroshima-Kyoto), you can buy Kyoto-Osaka ticket separately (less than 600 yen).
http://www.westjr.co.jp/global/en/ticket/pass/kansai_hiroshima/

JR West's Sanyo-San'In Area Pass is for 7 days and 19,000yen, 10,000yen cheaper than the nationwide JR Pass. The only thing you cannot do is take the shinkansen from Shin-Osaka to Kyoto.

When will you travel?
Maybe during a busy tourist season?

A Japan Rail Pass
(7-day Ordinary Class: 29110 yen, paid in your currency)
is not recommendable,
because it is much more expensive than JR regular fees for the itinerary planned at present.

Unless you are eager to reserve your seats
(even when it is not necessary),
a JR-West Kansai-Hiroshima Area Pass
(5-day: 13500 yen when booked through the website)
is suitable.
https://www.westjr.co.jp/global/en/ticket/pass/kansai_hiroshima/

This pass can be used
also for your JR Limited Express Haruka train ride without seat reservation,
on your way from or back to Kansai Airport [KIX].

In a case
where your Special Rapid train ride from Kyoto to Osaka or Shin-Osaka
is outside the 5 days of the validity of this pass,
you just pay 560 yen as the basic fare.

(This JR-West pass
is not valid on the Tokaido Shinkansen section Shin-Osaka -- Kyoto,
which is operated not by JR-West but by JR-Central.)

For the other way from or back to KIX,
you can choose
a JR-West Haruka discount ticket
(for your ride without seat reservation)
or a Nankai Kanku Tokuwari Rapi:t Ticket
(for your ride with your seat reserved).
https://www.westjr.co.jp/global/en/ticket/icoca-haruka/
https://www.howto-osaka.com/en/ticket/ticket/tokuwari.html