I guess that one thing they are achieving with 3-4-3 is higher value for PEY seats. The difference will now be noticeably bigger between Y and PEY.
Before the changes, I felt like with the 3-3-3 configuration, the PEY seats weren't that much of an upgrade.
With limited travel budgets I used to split outbound and return legs in J and Y much rather than going PEY both ways. Even though I have not tried the new configuration yet, Im quite sure that it won't be as enjoyable anymore. Apart from the slightly bigger seats you had before, one of the bigger benefits now gone was the ability to sit in D or G and possibly have the person sitting in E not disturbing you at all for restroom visits for the entire flight (lets assume the two sitting next to you are flying together).