From a business perspective I think day 1 makes the most sense. The fact is that many PC gamers only play on PC, similar to many console gamers playing only console. The percentage of people who have the newest PC and the newest consoles is actually quite slim (hardcore gamers are a small percentage of total gaming population). By putting your games on PC day 1 you can advertise to a much larger audience from day 1. If your game is a hit that everyone is talking about then availability on more platforms equals greater sales.
There are more factors than that. How much will same day PC releases impact console sales? The piracy factor plays into this. It's much harder to pirate a console game then a PC game. So they will lose out to console+PC gamers who opt to pirate a copy of the game instead of buying it on either platform.
Also, development cost, as a like for like port makes no sense as the generation progresses. PC hardware outpaces the console side, so you run the risk of damaging the brand with subpar same day ports that aren't optimized to compete with other contemporary games on the PC side.
So, you can increase development cost to optimize for PC, but it incurs overhead on a project that isn't guaranteed success yet, which increases risk. Considering they make a lot of big budget games, that's a lot of risk of the game meets commercial failure.
By waiting for the sales to plateau, they can pick from the titles that have bonafide demand. Since the games are old by now, they can get away with ports that lack polish against contemporary PC titles, because it's understood to be a legacy title, so the comparison is made to the console version from the past, rather than the best and brightest on the PC at that time. They can devote a smaller team to handle the port as well, which lowers risk, should reception be lukewarm on PC.
There are other factors, but it all depends from protecting the HW business. There's a lot of revenue that is tired directly to the HW. PS+ is an earner, and that service isn't going to fly on PC. Cannibalizing that to jump full force into PC swimming pool doesn't make a ton of sense. If they intend on maintaining the HW side of things, then same day releases just don't make sense. MS has never had the same success that Sony has had on the hardware side, so their interests are different. They see more value in services, so same day releases make more sense for them. That and Windows is their platform. They have a vested interest in furthering engagement with that platform. Sony going same day would move them into third party territory, which is the tricky business that sees even large firms like Bethesda being sold. Valve and Epic have avoided that by creating their own platforms in the form of storefronts, so I don't see Sony abandoning the rather lucrative platform they've spent decades building.
