Convenience of separate tickets vs JR pass

I am having a hard time deciding whether to buy the JR pass or just separate tickets. I found all my connections and prices on the JR west company website. Single tickets come cheaper than the 14-day JR pass by about 20 euros. I would buy the JR pass if it is more convenient. But if for seat reservation one must go to the ticket office, buying the ticket is not much more effort. Or maybe a combination of other passes could work, but there I would need some help.

My itinerary: I start from the center of Tokyo due to prior business.
day 1: Tokyo (center) - Kii Tanabe
day 2-6: Kumano Kodo trek
day 6: Kii Katsuura - Kii Tanabe
day 7: Kii Tanabe - Wakayama (stop for 2 hours) - Kyoto
day 7-11: stay in Kyoto
day 12: Kyoto - Tokyo
day 13: Tokyo - Narita Airport

What time of year are you going? At peak travel times, there can be really long queues to exchange the railpass at NRT, which you may not wish to do after a long flight.

If you're not going at a peak time, the chances are there'll be plenty of seating in the jiyuuseki section (non reserved) so making advance seat reservations may not be necessary, in which case the ease of using the JR pass is useful.

Consider too that while you're in Kyoto, you may wish to do day trips elsewhere, so having the pass could come in handy.

I am going from the 14th of May till the 26th.

When you've compared costs between single tickets and buying a JR Pass, have you included the cost of seat reservations?

They're only a couple of hundred yen at a time, but they can easily add up to the Euro 20 difference that you quote.

Your point about queueing to buy tickets isn't quite correct. If you're travelling in unreserved (and remember that local trains generally don't have reserved seating), you don't need a ticket. You can just go through the gates with your JR Pass. If you want a reserved seat, then you need to queue for tickets. However (either with a pass or without one), if you know your plans in advance you can buy all your tickets in one go (or buy the tickets for the next few days in one go).

For info, I've never had to queue for very long to get tickets. A matter of a handful of minutes. The time it takes a travelling partner to go and pick up drinks and snacks for the journey, or to pick up luggage from the coin locker where you've left it. Queueing for tickets has never felt like it's added to the total journey time.

As Bob says above, there can be a bit of a queue in Narita to exchange your JR Pass, but even when landing at busy times I've never had to wait longer than approx. 20 or possibly 30 mins. If you're not travelling on by JR train (e.g. you may well be taking a bus or a Keisei train into Tokyo, depending on where you're heading for), then you can always bypass any queue and exchange your voucher in Tokyo.

The other thing you might have a look at (I'm assuming you've made a list of costs for each journey in order to come up with the comparison in your original question), is whether there's any advantage in a combination of buying a 7 day pass for the period when you're doing the most travelling, and then buying single tickets for the rest of the time. This approach has worked for us on one trip.