I have Zeros and I love them. I don't have Quattros, but I do have Candy's on my mtb. I really prefer the Zeros. At first, they are harder to clip into, because the spring is tight, but within a week, they're loosened up. Also, when installing the cleats, you have to be careful not to overtighten the screws, because this will also make it harder to get into. I like them because the shape of the cleat guides your foot in. You just put your foot close to the right place and it slips right in. I guess with both, it's easy to pedal without being clipped in, like in traffic when you might need to quickly unclip.