Its also worth noting that one tiny change (as in, you wouldn't notice unless you really paid attention to the original game) is that Tamashiro's badge/emblem for his family was changed. The original version of the badge was quite close to the Imperial Japan flag. But no one really raged about that, just ignorant redditors yelling "SJW" because Sega dared remove some pretty bad content. Which is strange as they actually have a pretty positive trans story in the Japanese release of Yakuza 3 as well regarding the massage parlour lady (whom you might recognise as the lady from many of the Yakuza/Sega streams that Nagoshi does). So hopefully when 3 finally gets a English PS4 release we get all the stuff cut from the PS3 version. Well almost (we ain't getting Answer X Answer, and nothing of value was lost!)
1080p resolution (higher in Pro, not sure if native 4K). 60FPS frame rate, pretty much locked, bar one corner of the Sega Nakimichi arcade (no, really, it just drops there!)
Also, load times are basically reduced to 0 - so while its not as instant as walking into a shop in Dragon Engine games, its almost there.
Worth noting, that while the frame rate boost makes things gloriously smooth, its the res jump that helps most as the Yakuza games are almost all sub 720p on PS3 (bar Kenzan) an 3 especially is insanely blurry. Playing the same game but in a higher res makes certain areas really pop - Okinawa especially in the day time/sunset is sublime, textures really upscale really nicely to the higher res' and are much more readable to!
As mentioned above, aside from the side stories cut, the quiz game Answer X Answer is also cut. While never stating why, I have a feeling its due to Sega not wanting to localise the content in China/Korea (which got a same day release as Japan did for the remaster). So they made one version of game code instead of tweaking it for other markets. Aside from that I'e read in the past that AxA stores its questions as textures/image files and not text - so changing them to other languages is actually far harder than it would first appear. Then you have the issue that all questions are based around pop culture/history/niche content in Japan, so actually knowing the answers even if you speak the language would be difficult anyway.
Also, you can't look at magazine covers anymore in the M Stores. Oh well, nothing really lost there!
Also, interestingly unlike later Yakuza games which held auditions to get hostess girls for the games, Sega licensed real hostesses from real clubs (from what I understand) for 3. These licenses expired so they swapped the hostesses out for others from other Yakuza games. Fun fact, the dialogue/side stories/answers all actually stay the same as they originally were in Yakuza 3!
Oh, and one more change/addition is that all DLC for the game is now ON DISK. This includes all weekly DLC packs that just gave you more items, but 3 was actually the one Yakuza game that originally had DLC modes as well for the arena, as well as a survival/boss rush challenge mode. So all this is on disk this time which is fantastic.
I've not played 4 yet, but I put 100 hours into the PS4 version of 3 and I gotta say despite it being a pretty budget remaster (not in the same league as the Kiwami's) I absolutely loved it. The few changes they make (to res and FPS) make it an unquestioably superior game. And I enjoyed it so much that I actually got the mini game master trophy (anyone who's played Y3 will know that's no small feat!)