Corsair 100R comes with 2x AF120L fans, one at the front and one at the back. AF120L is upgraded version of AF120 fan. Since AF120L fans aren't available to be bought without a case, there are no official statistics about the fan and i can't tell if AF120L would do as proper case fan.
Usually stock fans are quite bad. I got 3x AF140L fans with my Corsair 760T case and i replaced them all. Even though they were silent, they didn't move much air.
Since 100R supports 2x 120/140 at front, i'd mount 2x 140mm fans at front. With bigger fan, you'll get more air moved with less of a noise. But if you decide to have 2x 120mm at front then it depends which Corsair SP120 fan you have.
If you have SP120 High Performance Edition then it would be better than Riing 12 since it does move more air with greater force, provided that you'll run it with full power (2350 RPM),
specs:
http://www.corsair.com/en-eu/air-series-sp120-high-performance-edition-high-static-pressure-120mm-fan
But when you have SP120 Quiet Edition, then the Riing 12 would be better since it falls short from the performance of Riing 12.
specs:
http://www.corsair.com/en-eu/air-series-sp120-quiet-edition-high-static-pressure-120mm-fan
Since i don't think you're willing to listen 37 dB(A), which SP120 High Performance Edition fan will do at 2350 RPM, it's safe to say that you should go with Riing 12 fans as front intake fans.