There is a difference between Su-30MKI program and FGFA program. Su-30MKI was a customized version of Su-30 with hi-tech features like TVC, better radars, canards etc. And Russians later used the same concept to export it to Malaysia, Algeria and even ordered over 100 units for themselves.
The Su-30 is actually the Su-27UB operational trainer. The Su-30M was given a better radar and was used by the PVO as a mini AWACS type aircraft to operate with lighter fighters as an airborne GCI vehicle.
The aircraft was used as the basis for the Su-30MKI because India wanted a multirole two seater aircraft and it was the obvious choice.
Apart from the addition of canards there wasn't really much of a structural change for the aircraft from the Su-30M design.
Most of the real changes was the internals and avionics and systems.
Where the FGFA differs is that it is not a customized T-50 based on Indian needs. It is rather a JOINT-VENTURE, where India and Russia are paying equal amount of money for complete R&D.
The T-50 is already pretty much designed... Indian money is not going to radically change it that much unless they want it to be even stealthier which might lead to increased purchase and operational costs.
At the end of the Day the difference between the operational PAK FA and the operational FFGA is that the latter will be developed in the directions India wants with the electronics and systems in it that India wants.
Current T-50 as per Sukhoi themselves is a 5(-) fighter, but FGFA is going to be a true 5+ gen fighter and Stage 2 variant of the vanilla T-50.
Sukhoi haven't developed a shell, they will have been perfecting fully integrated electronics for the aircraft for the last decade. The Su-35S will have -5th gen avionics developed for the T-50 and the first T-50 prototypes will have those avionics installed with improvements developed and ready for the first serial fighters.
India might go with those components or they might choose domestic or French or Israeli components too... Russia might choose some Indian made components but are unlikely to choose Israeli or French components for obvious reasons.
I don't expect the final Indian and the final Russian variant of the T-50 to be that different. Perhaps the Russian variant may have slightly better avionics and missiles, but even that has to be seen![/quote]
Better in this context is meaningless... India will get the avionics they want and the Russian AF will also get the avionics they want... there wont be better.
even Su-30MKI, Su-35S, and even stage 1 T-50 all have 2D TVC that is mounted in a ---\ /--- V-axis and can generate both vertical as well as lateral force, and can provide thrust even in the yaw plane(apart from the usual pitch axis thrust).
Hence some people call this kind of canted TVC as "virtual 3D "TVC, some prefer to call it 2.5D TVC.
The butterfly tail of the YF-23 with 45 degree tail surfaces can in theory simulate vertical and horizontal surfaces, but is not totally efficient at the job so they are not widely used.
TVC engine nozzles are the same... they allow some Yaw control at the cost of less efficiency with vertical and horizontal deflection effect.
Lets see whether they can develop something like that. Cause if they can, it would mean all aspect stealth like F-22 along with post-stall manoeuvring of the super-flankers(if not like that of Mig-29OVT)
My own personal opinion is that Full 3D TVC is more valuable than the minor advantage rectangular nozzles offers... note the F-35 does not have rectangular nozzles either.