I've used Zippy the most of all the DLC cars, it got me from silver to gold. It has certain firmness to it. I play a lot of hotshot and if I feel that hotshot is too light, I switch to zippy. Ripper has an ok turn radius but it feels kind of heavy and the handling isn't sharp enough for me. Scarab has a silly hitbox, but if I feel like playing a defensive ground role, I choose it. I find it really easy to make accurate longshots with Scarab and I often prefer those to aerials. Grog on the other hand is a heavy beast. It turns super slow, not loosely, but slow. If you need to do an easy 180° really fast, Grog says nope. It has a certain delay to powerslide, which makes it hard to turn fast. But if you keep a good momentum, Grog kind of shines. Just don't stop, and Grog can do a lot harassing, especially disrupting goalies and ramming into offensive ground cars. Plus Grog is phenomenal at those low-mid air close to enemy goal rebound balls, that are hard to shoot with flatter cars. But it does handle like a sedated elephant, needs a lot of advanced maneuvers to get the most of it, like the tumbling nose 180 turn (at medium speed: tap jump, point down, roll with powerslide, hit the ground with your nose and boost when the wheels touch the ground) and powerslide with boost (slight delay with boost; turns faster than just powerslide). I figured these techniques out myself but there might be better ones too, I just don't know them.

Tl;dr It all kind of comes down to playstyle. Dominus and zippy for aerials, scarab for longshots and ugliness, grog for driving fast and ramming and ripper for a heavy jack of all trades master of none. I didn't like Takumi at all. Some will have differing views, but these are my experiences and no one else bothered to reply your guestion.