S400 is no where near as good as our Aegis system. I know because I worked on it. The patriot missile did have some spectacular fails though where an anti-missile became confused and shot right into the ground
Although I will give the Russians props for possibly being the first nation to land the missile back in its own tube.
https://youtu.be/gNNkRuSw_0Q?t=52
Then there's also S500 now, which can shoot down anything that flies, including stealth planes, ballistic missiles, hypersonic planes, and LEO satellites. This is a typical example of asymmetric warfare. The US spends 1.5 trillion building a super plane, Russians spend 1/1000th of that building the thing that can make use of such a plane a costly proposition (even if it can't _reliably_ shoot it down), and offers it for export eventually, too.
Just like the SR-71 that flew over Russia with impunity because they couldn't hit it if their countries life depended on it. Oh, yea and we built that almost 50 years ago and you still couldn't hit it today. There are stories of Russias MiG aircraft just falling out of the sky when attempting to reach the altitude of the SR. Russians then built the Stainless steel Mig 25 which was then of course stolen and revealed just how bad the Russians are with metallurgy.
Or do you mean you worked on one of them and therefore can compare them (without experience of the other)?