Even s-400 has pesa I think.
But chinese have modified the s-300 to a great degree and the testament to that is the contract its clone won in turkey defeating american and russian systems.
On indian bmd vs s-300 we lack the mobitity and flexibility of s-300 and don't forget russians have way better radars than us(still).
Oh yeah,and what were the systems offered by other competing countries which The Chinese are claiming their HQ 9 won against??Lets take a look now,shall we??
1.The Russians were offering their S 300PMU dating back from around 1978 or 79!!Quite obviously they were eliminated.
2.Now lets take a look at the Americans who came at third.Their Raytheon and Lockheed Martin offered their Patriot Advanced Capability 3.Again a dated design with a somewhat dubious reputation even against ancient Iraqi Scud Bs.
3.Now lets come to the Europeans who came out second in the competition.Their Eurosam offered its Aster 30.It's a very capable and lightweight system with an unexpectedly higher range for its weight,but still it has shortest range and maximum altitude (at 120 km and ~20 km respectively) among the 4 competing systems.And the Turkish were specifically looking for a long range air defence system.
Beside,just like any other European systems,they are the costliest.
Now coming to the Chinese HQ 9 option,well it's more modern compared to what the Russians and Americans were offering.
According to the reports,the Chinese HQ 9 umderbidded the next lowest bidder (presumably the American PAC 3) by at least over half a billion to a billion dollar!!Now do the math.
Besides,the Chinese can offer a much more generous ToT than the others.
All these reasons made sure the Chinese to win the competition.
But world is not simply black and white,there is also a grey area in between.The Chinese winning the competition doesn't automatically transform the HQ 9 into a better missile defence system than the latest Russian or American or European systems!!They won due to a variety of reasons;but being the best was certainly not one of them.
And coming to upgrading or modifying the S 300 or any other system for that matter........modification can only get you that far.No matter how much you modify for example a S 300PMU2 missile round you can not increase its target interception altitude to 150 km or increase its speed to ~Mach 6 from Mach 4.Not without drastic design changes,which will turn it into a system altogether,which means you have to again rigorously test launch it over the years and you have to rework on its target interception algorithms - something that would be hardly economical.
Again,it's not true that Indian BMD system can not compete the Russian ones in terms of mobility.Why not??After all the missil launchers are mounted on Tatra or Tata heavy-duty trailers,so mobility shouldn't be that big a problem.
And coming to the radars,it's debatable when it comes to ground based AESA radars (and even AEW&CS ones as well),especially after this year's Defexpo where LRDE showcased variety of its latest ground based radars.