Although both programs are offered by prestigious institutes, I prefer CSE at MNIT to electrical at IIT Mandi. Considering only the branches it’s not a brainer that CSE offers much better placement opportunities than Electrical. I am not saying IIT Mandi placements are not good, it's just that they cannot be compared to MNNIT CSE placements.
I would suggest that you go for CSE at MNNIT rather than Electrical at IIT Mandi. Yes, you will miss the much coveted IIT tag but trading it with an NIT tag, better college life, and excellent placement opportunities is not a bad deal right? The moment you sit for placements and start receiving excellent packages in contrast to your counterpart electricals, you will realize how wise your decision to choose CSE was.