None of them.
In the fictional case that all of them would be open to sell, and to sell to Sony, and that Sony would want to buy pubilshers and would have enough budget to buy any of them, I'd buy before Capcom, From Soft, Square, MiHoyo and Bandai Namo before buying any western publisher.
But if we have to choose one publisher, I'd get Epic. They have Fortnite, Rocket League or Fall Guys. They make a shit ton of money with their games, but all that data and expertise would be also super helpful for their other GaaS teams, and would also help Sony in mobile and accessing a way younger audience. On top of that, they also publish games like Alan Wake and the next Fumito Ueda game.
On top of that, they have Unreal Engine: the most used engine by the AAA and AA games, but now also super important in cinema, tv shows and so on. An area that is also very important for other Sony divisions (cameras & Sony pictures).
The Epic Store doesn't have a great market share, but at least has an established PC store which is the biggest one after Steam and supports DRM. I think it could be adapted to be turned into the PC PSN store and launcher.
They must make a ton of revenue and profit, like Valve. But like Valve, I think they would be too expensive and that wouldn't want to sell.
I think that after Epic, Valve would be the top 2 western candidate: they'd get basically the biggest -by far- PC store plus the current PS Vita (SteamDeck) and the knowledge and catalog from their VR device (including HL Ayx) and a good back catalog with a few top IPs. So they could secure Half Life 3 as console exclusive.
Definitely makes them far more complicated. It's hard to see EA or WB being worth it unless there is a very clever way to work around the issues.
I think it's totally unrealistic to consider that Sony would buy Epic, EA, Take 2, Ubisoft, Valve or Epic because of thier pricing being too high and willingness or need to sell.
Regarding WB, they had certain willingness to sell, at least portions. I think they could be open to sell isolated studios or even isolated IPs.
Even without IPs, they have super talented studios that would be interesting to buy: Rocksteady, TT Games, Netherrealm or Avalanche. Netherrealm would be a great fit for Sony, and the other three don't make the type of games that are a top priority for Sony in terms of acquisitions but if priced at a good price they would be a great acquisition.