Time to talk about some basic details of the IEI products:
The Meraj-4 (Bavar-373) has a higher volume search performance than the S-400's 91N6 Big Bird.
It is also a hybrid ESA (similar to Ibris-E) --> a linear AESA (which Ibris-E is not) in transmit mode and a single element-per-element AESA in receive mode, whereas the 91N6 is a pure PESA.
It is much more compact than the 91N6.
The field in which the Big Bird is superior are ABM modes and its integrated sector scan mode.
Here the Bavar architecture splits this task to the dedicated Bavar-373 acquisition radar (taking the place of the 92N6 Chease board in S-400). The S-400 on the other hand uses the 91N6 by giving it a twice higher update rate than the Meraj-4 (two janus arrays) and allow for a sector search mode while performing volume search
Here Bavar-373 design philosophy goes another way and one statement is fact: Comparing both systems, the Meraj-4 has a somewhat longer detection range than the Big Bird. If upper echelon IADS information warns the S-400, it can track the target earlier by using the Big Bird in sector search mode.
However also the Meraj-4 could concentrate its energy (BT mode) on a specific sector if the target is given to it by IADS.
So the result is that in terms of hardware power, the Meraj-4 is higher performing than the 91N6, which is a huge achievement. Chinese even copied the Big Bird, while Iran develops its own solution. That solution is nothing highly expensive like a full element janus faced AESA but a very cost effective hybrid array solution.
Chinese (meanwhile) and Russian are masters in radar technology but Iran is catching up in a innovative way.