Yup, the difference between 9 or 10 across on the 777 is significant for many passengers. Just like 8 or 9 on the 787 or A330. And, while not flying yet 10 on the A350 or 11 on the A380, both of which Airbus is willing to sell versus the "normal" 9 or 10 those planes typically carry.
The bad news is that new 777 deliveries & retrofits are, more and more, seeing the 10-across option. LX just announced that it would do such on its 77Ws and, while not official from the company, UA is likely to do so as well.