I'm a real fan of high powered tuned cars. Between 500 and 900 horsepower is always great fun. Some slippery tires and trying to keep that beast on the track. Racing cars, especially those above 600HP can't really interest me for long. Way too much grip... So what do you prefer to drive in A-Spec / Online?
I like cars that either have perfect balance and good handling or cars that require lots of finesse and as a whole are challenging to get to do what you want. Challenging but also rewarding. Sometimes the whole question of liking or hating a car is all about learning to drive it so I try to drive more than couple of laps before deciding how much I hate it .
The jgtc/dtm cars are easy fun, nascar on roadies is a bit more challenging but fun still. Some fully tuned cars are more crazy than fun but meet the challenge requirement. Some cars like the light lotus vehicles are bit of both. They do bite if you get it wrong but really fun when you learn them.
I did some online races in the subaru sti something with the worst tires and it was surprisingly fun. The car is a bit understeery but with less grippy tires you can rotate the car if you remember to just brake early enough. And then again the tvr tamora was quite fun on chamonix snow.
So it depends really. I'd guess I could like the lemans prototypes as well but generally I like cars that rotate more and rely more on mechanical grip instead of massive aero. Also massive power tends to make the car behave kind of bad and breakneck acceleration doesn't work on many tracks. So it is track specific too.
I'd still say the sweet spot is somewhere between 300 to 550bhp . Depending on lots of things.