I would say 2990WX, it's lot more high-end build as well :- ). I went all out with the cooling and parts on it, with intention to get the most out of it in terms of performance (while keeping excellent acoustics). I've succeeded in that despite the baby pains with bios and software part.
The i9, I tried to build it in very budget way because I got the CPU for relatively cheap (1200 euro). But then I paid for delidding and the results were not stellar anyway. I would need a board with much more than 8 phases that my Asus has (all boards were like that for x299 with like three exceptions), and same powerful loop if I would want to keep it highly clocked (4.4+ Ghz) while keeping it silent (<30dB). I contemplated rebuilding it into custom loop as well, with better board. But then again, it feels like wasting even more money on it...
Neither is perfect as highly clocked i9 gets almost same performance in Corona compared to 2990WX with half as many cores only !. The difference is opposite in everything else (like Marvelous Designer simulation, etc..), so Corona perhaps runs against the memory limitations of Threadripper architecture.
With Dynamic Local Mode, single-thread performance should also feel pretty much the same in all apps as well (like working in 3dsMax and Photoshop, and it does, both feel equally smooth I would say).
For future, I still feel Threadripper will continue to get better because the IPC is getting up (Intel struggles and only rises clocks), the infinity fabric is improving, ram speeds are going up and costs will go down as manufacturing this architecture is relatively cheap.
But future Intel ? The "28c" i9, if it even comes to market, will be hugely overpriced, it requires 20+ Phases (the boards are ridiculous), will required crazy overbuilt water-loop (like mine, but not for high-overclock, but to simply get it running).
At this moment I am still lot more partial towards AMD :- ).