About as close to zero as you can get, at least in terms of audio quality. Any meaningful differences are going to be features and usability.
Go with any streamer as long as it works and then use a decent DAC.

I use a Raspberry Pi, works perfectly fine, it’s 50$ and easy to hide cause it’s small.

Depend how hard you believe in magic and in the positivity of electrons.

Yes. I’ve listened to all the Linn range of streamers from the Majik to the Klimax. I own a Selekt. The sound markedly improves from the lowest to the top. Even within the Selekt options, the new chassis and power supply with the latest model have far better sound quality than mine. That’s before any change to the DAC.

Yes. I own 2 iFi Zen Streams (Office and home), a Wiim Mini, a Wiim Pro, and have also have used two Macs and a Windows PC. The Zen’s (especially with a linear power supply) trounce the Wiims. The Wiims are a little better than the Mac Mini, which is a whole lot better than the HP Elitebook.

there’s only two ways you’d find any quality difference:

* handling of over-zero - lossy compressors sometimes decompress to “over-0dB”. playback software can choose to hard clip, soft clip, or limit. will manifest as a slight difference in harshness on very loud or poorly mastered material
* source rate conversion. players might handle mixed sample rate stuff differently (44kHz source vs 96kHz core). some algorithms work better than others often at a tradeoff of end-to-end latency. manifests as slightly different phase and response behaviour above 15kHz. if you’re over 30 years old you probably can’t hear differences up there.

apart from that, for the most part numbers are numbers, everything is buffered, and if it’s digital-in-digital-out almost nothing can go wrong.

Yes. Just last week, I ordered a wiim mini for my father and hooked it up to my system when it was delivered. Compared it to my node w/ upgraded lps. Not double-blind testing or anything like that, just a no-expectations a/b test. Only difference was that I used coax out from the node and optical from the mini. Node was noticeably better. The wiim just sounded thin and less dynamic. It wasn’t a massive difference like Bluetooth compared to a hardwired network, but it was definitely noticeable. Especially in the upper and lower frequencies. Cymbals kind of scatter off with the mini and had a more defined decay with the node. That was the easiest thing to pick up on. Bass was less pronounced. It wasn’t that it was quieter, just not as authoritative.

I have other opinions about other streamers I’ve heard, but these are the only 2 I’ve heard in the same system, a/b style.

Are we talking about something that outputs via USB or SPDIF/Toslink to a DAC? Other that jitter/clocks, isnt a digital feed a digital feed? The 1s and 0s cant be more 1 or 0

I bought an NAD CS1 streamer. It seems to be the only one that uses native software instead of their own. That’s a big plus for me.

A Raspberry Pi Zero (<$30) gives you a bit perfect, transparent streamer. The only reason to spend more is to get one with a built in DAC if you don’t already have DAC capabilities in your system. Or to get one with Dirac or PEQ.

Digital sources make a difference which is clearly measurable on the analog output of your DAC. Even though they all are bit perfect, differences in signal quality and timing can make a difference for your DAC. That is the reason DDCs exist.

However, modern DACs often have good buffering, so not all DACs react the same way to all digital sources. It also depends if you go with a USB or spdif connection. Some DACs are extremely picky for a good source, others don’t care.

So yes, there is a difference, it is measurable. But I would still recommend choosing your streamer on budget and Interface.

If you want more information, the YouTube Video of Golden Sound on the topics of DDCs goes into great Detail.