dining in San Sebastian
I can empathise in that there is so much written about SS restaurants on Chowhound that it is quite overwhelming.
If you read through a few of the threads you'll see very quickly that the difference between the three you've mentioned is very personal - you'll find people singing the praises of all of them but also those who were disappointed.
Some things to note:
Etxebarri is a fairly substantial drive from SS whereas the other two are in or within 15 minutes of the city centre.
Everything at Etxebarri goes on the grill - so it is a marriage of incredible ingredients with very simple (but still genius-level) cooking.
Akelare has a wonderful location with beautiful views.
Arzak is sometimes seen as very traditional in approach (some people rave about how friendly Juan-Marie is, while non-Spanish speakers often say they feel they were treated like second class diners).
I would type the name of each restaurant in the search window on the top right corner of this board as there have been many many post on the three restaurants. Not many in the past couple of months but if you go 1 year, you will have plenty of reading material. Below is a link to help you get started.
Etxebarri is very different from Arzak and Akelare. It is a county restaurant that specializes in grilling and great products. The other two are molecular/modern fine-dining restaurants.