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The MBPro will obviously be faster...

For the case of the i3, agreed. I'd happily take a base 16" MBP over the i3 Mini if price wasn't a concern. If we're looking at other configs, it gets a little more complicated.

For GPU-bound tasks, the MBP will have a clear lead over a Mini, except when the Mini has an eGPU. It's no contest. But pair a Mini with a desktop GPU and it gains a clear lead over any MBP config.

For CPU-bound tasks, it's been a bit like this for me in testing: i5 Mini < i7 MBP < i7 Mini < i9 MBP, which is about on par with benchmarks. But keep in mind these gaps are surprisingly thin. The experience here is all very similar.
 
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