What is the main difference between 1.9:1 and 1.98:1 ratioroller rockers? Which one is more preferred?

The main difference between the two is that the 1.98:1 ratio rockers open up the valves more, which is reflected by the noticeable increase in power output over the 1.9:1 ratio rockers. Unless you're the kind of person who isn't shy about taking your car to redline on a consistent basis, then the 1.9s would be more suitable as they make a little bit more torque down low than the 1.98s.