Such comparisons are usually made on the basis of ranges. When he say S-400 equivalent, i suppose the ranges are compared, not the mission profile. I believe that Turkey will follow the NATO strategy. Therefore, instead of a huge air defense system that can only hit air-breathing targets up to 400km range and limited missile defense capability, I believe a missile defence system which will have advanced ballistic missile defence capability and that can work together with Siper air defense family are developed based on Siper experience. While Siper cover the altitudes up to 30-35km, This new system will expand the protection umbrella up to 100-150km in altitude. The "Long Range High Altitude" missile which was once called GUMS and later stated to have being developed locally will be the missile emphasized as "S400 counterpart" However unlike the S400 mission profile, I think that this missile, with its dual mode seeker and DACS-controlled KV load, will perform both air defense duty at longer ranges and missile defense in an exo-atmospheric environment when necessary like THAAD. This is my prediction. We will wait and see.
Let me give you my understanding about russian missile defense "Concept".
Back then 70-80 and 90s russian had/have S200, S300 (and other lower layer missile platforms like Buk,Tor etc. ). Which WERE uptodate according to Military options of Attack via Air.
But after 1991 we saw that us used new tactic and it is like following .
From Long range 350+ km They deploying BIG air Plane (not fighter) and main purpose of plane/s are to provide Real time situation awareness and deploying NEW inovation missiles. This missiles can MIMIC fighter or use as decoy or use as ECM or use as JAMMING and making spots unvisible for enemy EW!! AND this was A THREAT for any avilable russian missile defense. I mean This Plane is out of range and it is deploying platforms which Actually have Tech and Tactical advantage which lead to russian to lose.
Therefor russian saw that tactic and others in IRAK war. So russian had to update missile defense systems with NEW tactic to counter the new us air attack tactic.
russians decide to build new system s400 which have increased range missile to reach 400km to chase or stand off those Planes. Therefore they also updated radar range also they updated satellite radars too.
So The MIAN purpose of s400 is still countering above us tactic depolying BIG FAT plane around 400km and making attacks from there. s400 main/primary objective to counter the new air attack us concept. It is not made to engage fighters or missiles at long range forthat russians have other plaftorms for that.
I think Turkiye bought that s400 because of us threat which was Real back in 2017-2018 when us were really aggresive against Turkiye