Feels like a downgrade as even the 3950x is behind the 9700k in raw gaming performance, I just need the extra threads for frame time stability and multi tasking
but your only talking around 4-5% faster real world use (gaming manly) compared to a 3900/3950x and the AMD platform has room to upgrade which z390 doesn't, i mean sure you can go up to the 9900k/kf but after that you need a new platform.
AMD has always excelled at multi thread performance, it was good on 2nd gen ryzen and 3rd gen is a pretty nice boost to that, plus with added support for fast ram on 3rd gen its a very tempting option that should be high on your buy list. We don't know quite yet what intels 10th gen will bring to the table, from initial looks it is still behind in multi thread tasks compared to 3rd gen ryzen, yes gaming looks to improve on 9th gen but at the cost of high power usage, although thats not confirmed yet, just look at the new z490 mobo's most have active cooling on the vrm's which isn't and encouraging sign for the chips.
and worse news for Intel, AMD are said to be releasing 4th gen ryzen before the years out, putting even more pressure on poor old Intel