In my side by side testing of Whisper and Parakeet in transcribing Euro-English meeting recordings, Whisper produced the better result, but Parakeet was faster.

I'm sticking with Whisper as it is fast enough for my use case.

Does it need a newer GPU? Or can it run on just CPU?

Would it run on a raspberry pi?

Look up for faster whisper or distilled whisper models, smaller models run quite nicely but perform poorly outside of English, if you are interested in a different language it's better to finetune it (HuggingFace has a huge amount of finetuned Whisper models).

Best CPU TTS that can run on something like a raspberry pi is Piper. It can do real time synthesis on a raspberry pi and on a real computer it runs several times faster with negligible performance cost. I use it for 'reading' ebooks when my eyes get tired. The quality is roughly on par with where Mac OS's TTS was ~10 years ago (the last time I used it.) You can tell it's TTS, but it's good enough that you can become accustomed to it fairly easily.

https://github.com/rhasspy/piper

They are talking about STT, not TTS, but as a TTS piper is very good and works nicely on a raspberry pi, I agree.

What voices do you recommend? The ones I had checked out (about a year ago) - the voices were mostly european-sounding, and flat, and not so natural-sounding. Is Piper the best open-source text-to-speech engine out there?

You can also try Kokoro and Sherpa.

If this is for personal use the best local TTS is to grab a Mac, set the system voice to one of the current Siri voice models, and then use the 'say' command in the terminal. Yes, really. The nonbinary voice #5 in particular does really well at technical terminology.

If you want real-time, it requires a GPU, but can be underpowered. CPU is a little slower but works fine.

are there any linux/mac apps that allow people to use parakeet for daily dictation like SuperWhisper?

Sort of, check out https://github.com/senstella/parakeet-mlx.