Whenever possible, I now choose to upgrade to more legroom on international and domestic flights. I’m 5’2” so it isn’t about the room for my legs, it’s about not feeling boxed in, in particular when the person in front of me reclines their seat. Just a few inches makes all the difference in feeling more comfortable and less stressed. My husband and I also choose aisle seats across from each other when the seat configuration is 3 and 3.
FWIW I’ve flown Icelandair in both economy and recently in Saga class (when we found a screaming sale). We enjoyed the roomier seats, smaller cabin and meal service, which is comparable to US domestic first class. On Icelandair in the future though, I’d upgrade to more legroom in economy for sure, but I wouldn’t pay full sticker price for Saga.