First off, some general information on PS5 vs PS4.

1. PS5 doesn't look to be that much faster than PS4 with SSD. The largest benefit appears to be in the immediate intro (similar to P5 Vanilla), where you receive approximately a 5-10 second advantage over PS4, possibly due to this being before caching starts kicking in. Very similar to the HDD > SSD jump, the immediate intro seems to be the only largest noticeable difference. Everywhere else appears to be frames at best. It is, however, nowhere close to the jump that you get moving from the stock HDDs on PS4 to any kind of SSD (External/Internal), as loads aren't observably that much faster. Some even appear to be slower, without much explanation. I will detail one that I have noticed later.

2. PS5 does not have any effect on the "slow casts" you will sometimes get during battle. Proving these aren't due to any kind of slow loading on spells, but just a general flaw of Persona 5.

3. Using PS5 does not appear to remove the faster load benefits received from caching during play. Loads being slower after booting the game fresh still exist.

4. There doesn't appear to be any observable differences in Shadow A.I, collision, etc on PS5. Gameplay wise, it appears to be identical to PS4.

Considering how much time I've put into the game and shadow behaviour, any changes would've probably been apparent to me immediately.

5. Swapping controllers is quicker on PS5 than it is on PS4. As in, if you were to be using a turbo controller and wanting to swap to the dualshock 4 for the darts game, it it quicker to so on PS5 than on PS4. Not by that much, but still quicker.

One load that I have noticed (multiple times) appears to be actually slower on PS5 is this one:

PS4 Example (69 frames)

PS5 Example (73 frames)

This one was largely noticeable to me due to the 'Take your Time' logo actually appearing, which I had never seen on my PS4 during runs, but have multiple times on my PS5. Even during another run which I have no longer have footage for due to it being a failed attempt, the logo appeared. I haven't noticed many other instances of this, however they may well exist, as the only reason this particular load caught my eye was because of the 'Take your Time' logo showing.

The Flower Shop loads look to be generally slightly faster, however it is also difficult to use direct comparisons here because it appears that the actual NPC that shows up to the flower shop (of which it appears random which does) can seemingly cause a slightly longer load sometimes. The general observation I've made however is that the PS5 looks to be faster here, usually by a few frames.

(These are timed from the first frame the screen is completely black after selecting work, to the first frame the cutscene becomes visible)

6/18 Flower Shop Comparison

PS4 (89 frames)

PS5 (87 frames)

6/22 Flower Shop Comparison:

PS4 (93 frames)

PS5 (90 frames)

The Bathhouse also looks to be a very similar situation.

4/24 Bathhouse Comparison

PS4 (103 frames)

PS5 (102 frames)

6/6 Bathhouse Comparison

PS4 (107 frames)

Warping between locations looks to be slightly faster only in some instances.

Warping from one area to another area seems to vary. Status Warping to the Hideout seems to be faster on PS5, however Status Warping from Station Square to Central Street seems to be exactly the same between the two.

The difference when warping between areas in the same location is sort of inconclusive. PS5 etched ahead by 1-2 frames in two of the examples of warping from the 2nd-Hand Shop to Outside LeBlanc, however in the final example they're exactly the same.

Status Warping to Hideout (Timed from screen going black to the FFWD/Auto icons showing up / Game becoming visible)

6/3 Comparison

PS4 (57 frames)

PS5 (55 frames)

11/25 Comparison

PS4 (53 frames)

PS5 (49 frames)

Status Warping between Station Square and Central Street

9/4 Comparison

PS4 (16 frames)

PS5 (16 frames)

Warping from 2nd-Hand Shop to LeBlanc Comparison

Timed from first frame the 'confirm' text disappears after confirming the warp, to the first frame the game appears after going black; due to the nature of it being difficult to tell with the transition effects

5/24 Comparison

PS4 (40 frames)

PS5 (39 frames)

6/2 Comparison

PS4 (40 frames)

PS5 (40 frames)

6/7 Comparison

PS4 (41 frames)

PS5 (39 frames)

Warping looks to vary depending on the where you're warping and the method used.

Warping to the hideout looks to be slower on PS4 than PS5, however warping to Central Street from Station Square looks to take the same amount of time, no matter the console.

Other locations I've noticed a difference in was warping to Takemi's Clinic, which seemed to be a few frames faster on PS5 than on PS4.

Overall, I think PS5 can edge ahead in a few areas by frames but it isn't going to add upto anything significant. At most, a minute maybe across the run, if even that. Certain loads being only 1-3 frames faster in parts essentially means you would need to accrue hundreds and hundreds of loads across the entire game to even have it be a minute faster.

2 frames saved a load = 15 loads needed to save 1 second. Meaning to save a minute you'd need 900 loads (15 x 60), which... I just do not think is happening, even in a game this long. If you increase the average frames saved to 4 per load that'd still end up being 450 loads needed to save just 1 minute.

Does this mean PS5 runs will be legal now?

I originally asked about this 6 months ago and you said to just wait until you can get your hands on one. Now that you finally have the full PS5 info and have concluded that there's practically no difference, I don't see any reason as to why it can't be added as another platform, especially since the world record is on it.

I don't make the decision on that, though the other half reason was just the difficulty in acquiring one.

I've had one since August and have spent my entire time with this game since then on PS5, so this was largely just to conclude that performance/behaviour wise there's no difference between PS4 and PS5, outside of a very, very minor load difference in some scenarios, which was largely to be expected anyway.