What got me to commit to a regular race schedule was a good crowd of cool people willing to help a newb as I was.
Off-Road was fun to play with, but I didn't enjoy the racing so much.
Around 1989 a bunch of 12th scale racers in So-Cal took me under their wing, showed me what to do, and it's been my favourite form of RC ever since.
Simple, low cost, fast, fun, 8 min races
Sedans are cool, I like the way Tamiya does it with the realistic bodies, don't care for the hardcore sedan racing, way too much to deal with, too much like a full time job that doesn't pay well
So, if I were new coming into this hobby, something that looked cool like F1 or TCS racing might get my attention enough to stick around.
We do a lot at our local tracks to help the newcomers, and that makes the most difference to keep them coming back.