The number on the strut is the dampening ratio of the strut. The 90/10 only dampens 10% when the strut extends which throws the front of the car up. Then it dampens 90% when the strut starts to compress, which brings the front of the car down slowly.
The 70/30 will not throw the front of the car up as quickly but allows the front of the car to lower at a faster rate.
The 90/10 is strictly for a drag car with no front sway bar and the 70/30 is a street/drag setup and you can keep your sway bar. .