It's a little funny to see the "use AMD!" comments --- since from what I understand, Intel's optimisations that lead to these side-channels are specifically for performance, so using AMD instead of Intel might mean the same amount performance loss.
By contrast having to deal with the issue in software or worse, by turning off SMT, is much more damaging and gets you the 10s of percents of performance impact that people are talking about.
Go with Intel and risk losing a huge chunk of your performance some day, or go with AMD and know what to expect. Different people and companies have different risk tolerances, so it's not an obvious choice one way or the other.
From Zen thereon, they've been more or less on par in single threaded performance, and have the performance edge on multicore performance, while being cheaper and unaffected by most of these new CPU vulnerabilities, on top of that.