As a proud owner of both, I say it's a hard toss up between the 4,1/5,1 and the 7,1 -- but I voted 7,1.
The 7,1, because it is an absolute engineering masterpiece, brilliantly designed, and it just feels oh-so-premium to the touch. Yes, it was priced way too high for what it offered, and it should have come with PCIe 4 from the get-go and a more recent CPU, but it is what it is, and I accept that. For my current workstream it absolutely gets the job done, and then some, but I know others that need/want more power.
The 4,1/5,1 really is in a class of its own because it has been able to withstand the test of time for ~14 years (thanks to the members of these very forums). I was so happy when Syncretic patched the 6k series and
I was able to put an RX-6800XT inside my 4,1, before I upgraded to my current 7,1. Although, I am really am curious to see if Syncretic & co. will be able to fix the AVX2 emulation and get Ventura running smoothly on it, which will then further increase its lifespan, and the same with macOS Sonoma.
But frankly speaking, it is
extremely impressive that the 4,1/5,1 has lasted
this long. I hope the same happens for the 7,1, though due to the T2 chip, and pricing (which means not a lot of people/devs can get their hands on it), I am less optimistic, but we will see.