Recently travelled in both 12245 and 12246 - 3A in both directions.
Some observations:-
Coaches: The rake of 12245 in which I travelled had LHB like modular grey and white interiors with blue berths. Also, the coaches would jolt every now and then just like Howrah New Delhi Rajdhani Express.
The rake of 12246 in which I travelled had ICF like beige interiors with...
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brown berths and beige-ish air vents. It also had one fan in every compartment in 3A. No sudden jolts in this one. The exterior was same as the above rake with big windows and 72 berths.
Reliability: 12245 late by 1 hour and 12246 late by 2 hours. 12246 was delayed due to Odisha bandh.
Speed: Great! 12246 made three overtakes post Kharagpur at full pace.
Food: 12245 had plain food, 12246 was tastier, both good though. 12245 had ice creams for dessert all the time. 12246 had a broken fridge so gulab jamuns except ice cream of day 1 dinner at 5pm. I took veg food. Non-veg may differ. Fellow passengers were happy though. 2 bottles of water, one immediately after departure and another in the evening. For the third, you'll have to pay Rs. 15.
Other: 1. At Kharagpur, the trains slowed down so much you would think it would stop there but it didn't in either direction.
2. At Renigunta the trains stopped at the same platform, both 12245 and 12246.
3. One person per coach serves food. He expects tips after your day 2 lunch. If you're sleeping, he won't leave until he wakes you up and gets the tip!
4. 12246 was standing at platform in Yesvantpur well before 9:15 AM. Boarding was not allowed until 10:35 AM.
5. My rake of 12246 had automatic inter-coach connecting doors! Not working though.