Emulation on PC is clearly more versatile and, allows you to do things not even possible with the original hardware, like upscaling, using network play, using replacement hi-res texture set, etc. And of course, you can emulate more modern systems, like PS2, PS3, Dreamcast, Gamecube, Naomi, etc.
However, even if you setup a dedicated PC or a Mini-PC for emulation, you still have lots of maintenance to do and lots of complexity to deal with, like choosing between multiple emulators that are started in different ways (Retroarch, non-Retroarch, Mame, etc.) so you usually need to track down configuration files in many different places, so it's a lot of extra work, and you also need to do lots of OS maintenance as well. PC usually draw a lot more power and, in general, require proper modern video cards and fast CPUs to emulate modern systems, which is the main reason why you'd want to use a PC for emulation. You might already have a gaming PC, so that might not be a big issue, but if you want to setup a dedicated PC for emulation, it might be a fairly expensive proposition. Again, if you want to emulate the more modern systems only a (good) PC can do (like PS3) or heavily upscale systems llke PS2/Gamecube/WiiU, etc.
If your goal is to emulate 90's and before retro system, a gaming PC is really overkill, a Raspbery PI might be a better choice (RPi-5 can do PSP, PS2 or GC, even if not in 4K), because portability, low-power draw and it might sit nice either on a desktop or close to a TV.
However, I think the Raspberry is plagued by the same issue of a full PC, and it's the bloat put in the user interfaces, wasting lots of cpu cycles and memory just to make a fancy interface with game covers, borders, preview videos, external attract modes, and all that stuff that is nice to look at, but it comes with a cost in startup time and taking away resources in general.
I bought every single Raspberry version as soon as it came out so, of course, when 5 came out, I had to buy it and yes, it is a powerful little machine but, the two main distributions that supports it, Batocera and Retropie (still in beta), are so bloated with stuff they become very confusing to use, especially when something doesn't work as you expect. Batocera is easier to install, but it's too inflexible if some emulators don't comply with its own configuration system, Retropie is more flexible, but it has so much going on, that you can easily get lost in the settings.
Then we get to the gaming experience: people say emulation lag can't be detected by normal users, but why when (after several years of being accustomed to Mister), when I first tried my new RPI5, almost every emulator I tried felt "wrong" and "disconnected" ?
It's some kind of placebo effect: since you know there's some extra lag, you start to feel it, no matter how small ? I first suspected this, then I saw videos showing how latency can affect gameplay, like in the infamous chase in Battletoads or the issues with Speedy Gonzales so no, I don't think lag is just something "in your mind", it exists and it can affect actual gameplay. Some cores that are very accurate on Mister, the lack of lag is a clear advantage.
Ease to connect to a CRT is a big advantage as well. Sure there are ways to connect a PC or an RPI to a CRT, but Mister is way easier.
SNAC is of course a big advantage: there's something magical about being able to use the original controllers directly, with no conversion whatsoever, so if you combine CRT + SNAC, you basically removed any extra lag. But it's not just lag: it feels authentic being able to use even weird controllers like Namco PSX Jog Controller, or Lightguns. I even managed to use a NES Powerglove, to be sure it was working correct before I sold it...
