I am not sure how unpopular of an opinion it is, but Group B seems to be the more popular of the two around these parts. But I have always though Group C was just more badass. I guess I am going to rant real quick like.
The cars were more powerful. A lot more powerful. Like this Nissan RC90 that makes over 1000hp. That wasn't just in qualifying either. Most of the cars were above the 700hp, while others were close to 800+! It was all based on how much fuel thought thought the engine was going to use.
There was variety as well. You could make an engine with as many or as few cylinders you wanted, you could make as big as you wanted, and you could add FI if you so felt the need. You had 7L V12, 3.5L V10s, turbocharged 4 cylinders and flat 6s, big V8s or small V8s, and even a very popular rotary. There was nearly everything for everyone
Plus the cars look like spaceships. They look good to everyone. Group B cars look good to enthusiasts, everyone else just thinks they are horrible monstrosities. Not to mention all the teams in Group C. There was Ford, Jaguar, Dome, Mazda, Toyota, Nissan, Porsche, Lamborghini, Mclaren, Peugeot, and a lot more!
I think one reason why Group B is remembered more fondly was that it was ended a bit early. While Group C lasted for more than a decade, where Group B was around for only 4 years. Plus by the end, the FIA made it so you had to basically use F1 engines. So the class was spending F1 money without the money that F1 gets.
I decided to add some videos to spice up my not so great writing!