Interested in the TS5 Plus for the 10gbe but wondering if that $500 is better put towards an M4 Mac Mini with 10gbe option.
Sometimes an 'apples to oranges' comparison is interesting and worthwhile. That's a good question. Let's take a look.
1.) You didn't say M4Pro Mac Mini; if you go with the base M4, you get Thunderbolt 4, not 5. That dock is a Thunderbolt 5 dock. Do you already have a computer with Thunderbolt 5 capability?
2.) Most people looking at this dock probably already have a computer. What, if anything, do you have? Will the Mac Mini be redundant, or render your other computer redundant?
3.) How long do you tend to keep a computer, and how long do you tend to keep a dock? If you bought the TS5 Plus, is it likely you'll use it with 2 computer systems in a row?
4.) Do you mainly use a dock with one computer, or 2+? This matters because a TS5 Plus can be switched from, say, a Mac Mini to a MacBook Pro, by moving the Thunderbolt 5 cable between them. A 10 Gbps ethernet port in a Mac Mini is...usable only by that Mac Mini.
5.) How many peripherals do you wish to hook up by cables? The Mac Mini has a decent selection of ports, and a much cheaper USB-C hub, or older Thunderbolt hub (like my CalDigit 3 Plus picked up for $90 used) can add to it, but the TS5 Plus adds a whole lotta ports.
This may sound weird, and I may be totally off, but I suspect the people who budget around $500 for a computer, such as the Mac Mini, probably aren't in the market for a $500 dock. Maybe M4Pro Mac Minis spec.'d up, Mac Studio and MacBook Pro users, but those aren't people paying $500 for the Mac.
Oh, and at the low end price-wise, that Mac Mini probably comes with a small SSD, so don't forget to factor in the cost of an external SSD enclosure and SSD to stick in it...at today's grossly inflated SSD prices.
For that matter, getting back to your question, if you are a user ready and able to take advantage of 10 Gbps ethernet, will you be happy with a $500 Mac? Maybe so, I'm asking. I tend to associate 10 Gbps ethernet use with higher end power users who'd likely want more, but even if I'm right not everybody is 'most people.'