There will be minimal difference between the upgraded Shatabdi and Tejas.
It is better to upgrade the existing branded trains like Raj/Shat etc rather than introducing new brands. There are already too many brands on IR network Raj, Shat, Duro, GR, Yuva, SK, Rajya Ranee, Jan Shatabdi, Jansadharan, Antyoday, Humsafar, Tejas and the proposed UDAY.
-
Basically following five classes of trains are...
more...

required
Class--------Max Speed------Avg. Speed--Type of Rake----------Coach Classes-- (op) means facility in select trains only.
Passenger--090-100 kmph--25-40 kmph-EMU/MEMU/DMU------GEN(op), SL(op), ACC(op), ACIII(op)
Express-----100-110 kmph--40-55 kmph-ICF existing coaches--GEN,IIS,SL,ACIII,ACII,ACI(op),ACC,EC(op)
SF-----------100-110 kmph-- > 55 kmph-ICF existing coaches--GEN,IIS,SL,ACIII,ACII,ACI(op),ACC,EC(op)
SF Deluxe --110-130 kmph-- > 55 kmph-LHB+better amenities-GEN,IIS,SL,ACIII,ACII,ACI(op),ACC,EC(op)
Premium ---130-160 kmph-- > 55 kmph-LHB+better amenities-ACIII,ACII,ACI(op),ACC,EC(op)

* Rajdhani , Shatabdi , Duronto (except a few Duros which have SL coaches too) , HumSafar, are all basically ac Premium trains provided with Generator cars
* Sampark Kranti , Jan Shatabdi- are basically SF trains-
* Jan Saadhran is basically travelling in unreserved coaches in Express and SF trains.
* Optional Catering should be made available in all the trains equipped with...
more...

PCs.
-
* Many branded trains like (Durontos, GRs, Shatabdies) are running with very less number of coaches causing a huge loss to IR. It is better to have as many type of coaches in trains as possible as per the class of train, so that more and more paxs could avail those trains and IR can earn more revenue from train.
* For example, Kolkata-Patna GR runs with just 7 ACIII(E) coaches and 2 generator cars which can give a very less revenue to IR and hence it is a highly loss making train. If ACII, ACI, ACIII coaches are added to it the revenue shall increase. But this train shall still require some SL coaches also to make it run with 20-24 ICF coaches.
* Mumbai-Ernakulam (LHB) Duronto operates with 11 AC coaches+PC+2PowerCars, its revenue can be increased by attaching 7-8 SL coaches.