I'm at about 71% and that's enough for me (actually it recently cranked up a few percentages of a percent even though I didn't do anything, I don't get that).
I notice that the Bullet damn near stops spawning after beating the game, some thought it was a glitch that it stops spawning after you're done with Simeon, but I was still able to find one later on.
Vapid Bullet is easily my least favorite Super Car, it's traction sucks, it's breaking sucks, it's speed even sucks (compared to the other 6 Super Cars, the Coil is the next worst Super, and that even smokes the Bullet).
I see Bullets and Infernus' all the time, it's actually annoying. The most abundant Super Cars I find are the Coil, Infernus, and Bullet. Out of these three, I'd go with the Infernus. But at the end of the day, it doesn't matter. I already have all 7 super cars in my garages and safehouses, 4/7 are with Franklin. 2/7 are with Trevor, and 1/7 is with Michael.
Also, I think I own ever single "Sports" car too, except for two. The Futo and the Sultan, and both of these look awful imo, they could be more "rare" than other Sports Cars, but I don't like them at all, so I don't need them.
I think I also have the best Sports Classics (JB 700, Z-Type, and Monroe) - The other few Sports Classics are SO slow and look like sh*t, imo.
I don't have the BEST Muscle Car, but I have my favorite, the Sabre Turbo, through speed tests on Youtube, the Ruiner is the fastest. I NEVER seen the Ruiner yet, as well.
And for Coupes, I have only the Ocelot F620 which is not the best, but I love how it looks and customized it, plus it's super rare to find on the street how I found mine (and what do you know? I always see them now, lol) and I have the Cognoscenti Cabrio which is in the top 3 for Coupes. The best is the Exemplar in first place with speed tests, but I rather the Rapid GT, which I got now, so the Exemplar is gone.
I don't have any SUV's, Sedans, or Compacts, I like fast and cars for looks, and of all these classifications, the cars are just awful and too damn slow.