Kids, Its been discussed. Technical details aside, discuss the purpose of these tanks. Take out the fact the tactical nukes PA intends to use against Indian armoured columns you realise many interesting notes.
Lets do a list of FACTS!
1)T-90 is MBT of India. Ordered in large numbers, will stay as the workhorse and compliment/replace the T-72. Minimal logistics change required as well as training, since 70 percent commonality with the T-72 which India makes 100% in India. The T-72 line at Avadi, got upgraded with ease to handle manufacture of T-90, some parts are still imported from Russia/France etc... until domestic production takes or will never be built in India as it'll add to the cost, example being the targeting system for now.
2) T-90 is a medium weight tank! its use is limited but strategic mobility is decent, can be flown via Il-76 transports give or take payload and stress better yet is the american transport for this purpose, would be able to move 2/3 at the same time! So its a tank that can be where needed, be it Punjab, Tibetan plateau or deserts of India.
3) Its not expensive, the above facts leads to low cost hence it is fielded in large numbers, its weight is low, naturally so is the cost. Its easy to produce and cheaper than the Russian variant, given the IA version doesn't use active kills. The Shotra system added to the expensive with out nominal increase in defence. This is one of the most cost effective tanks out there, especially the Indian variant. The APU is just a spare battery for the sensors, but turret is pretty much idle. No bells and whistles, just TANK!!! Notice it pretty much has the same features/ performance as the AK,Type 96/99, give or take.
4) While the hallmark of any tank is survivability in the field against heavy fire, this tanks survivability is not as high as you would expect. That being said, its also one of the most over rated tanks in the world thanks to large Russian fanboy PR and BS. It still has the same flaws for the most part as the T-72 and the same advantages. Thats notable. But field them in large numbers, itll get the the job done regardless.
Now nowing all this, what are the problems? Well the T-90 was designed for Russia, performance in desert areas like Thar has been problem for the crew. Well established fact. This needs to be addressed and the Army intends to fix this during the MLU phase of these tanks. Armour may be added, best way to protect the tank even in low intensity conflicts. This tank is here to stay, flaws or now flaws. The purchase of the T-90 was a long coming, it was a logical decision given that the T-72 production already existed in India. Avadi could have tested a new varient of the T-72, but this would need additional funding and they would hit the same target as T-90 pretty much. The T-90 saved India a lot of money in logistics/ training. Why RnD in house when off the shelf full TOT is available at low cost? It was a frugal decision by the finance dept. Besides India already has a tank project, that was needed.
You see, India looks at tanks, much the same way Airforce looks at its fighters. Light, Medium, and Heavy. China does the same as far as I can tell. This is due to strategic mobility of the weapons system. The old school of though of a single MBT is dead. The soviets used 2 teirs remember. Only NATO made this notion of MBT and forgot about weight. India is not NATO!
India requires 3 teir tank solutions. The medium tank already is avalible off the self from Russia, the light tank ie T-72 is exiting and needs replacment with a lighter tank that can be airlifted by smaller aircraft or helecopters. The only tank not sold to India is the heavy MBT that exist with NATO and its allies. India does not or did not access to these weapons. Hence the Arjun project. The light tank it seems is low prority given the T-72 will be up for the job for some time and off the shelf solutions are avaliable, the Russians/Soviets also have these tanks ready for sale and TOT if required. Not many are required though. Its a niche item for the airborne brigades.
The T-90 will only get heavier, and begin utilizing more technology developed for the Arjun. Arjun is also here to stay so long there is requriment to scare the PA. Arjun like its NATO counter parts, is offensive tank, meant to handle extensive damage.hits hence the heavier weight for the armour, the new mine plow should give these away as a spear head tank. The newer versions get even heavier armour, and so forth.
I hope this analysis helps in understanding the mentality of the armoured cores in India and around the globe.