I use an older Ribtect 2 vest, and it works great for me. It’s my experience that you want something rigid to take & disperse a bunch of the energy. The Ribtect 2 has a hard (Carbon Fiber) outer shell, and some dense padding on the inside. Ive tried some other rib protectors that are just dense foam and I didn’t like them, found they put too much energy into the body, and I would step out of the kart feeling sore. I’ve used mine for solid 6 years now and it’s still going strong (the carbon is showing signs of stress cracks, but nothing has broken yet) and that includes several rough parking lot races. I don’t use the ribtect seat, just the vest and a standard Tillett.
I havent tried the latest (Ribtect 3), but if its anything like the 2, its a quality product…can’t recommend it enough! Racing (and living) with sore ribs suck.