I don't have experience with them myself, but here's a review that compares them both
Review Conclusion: "Despite their similarities and identical B+ ratings, Reflex and Sonic are definitely different headphones. Pick Reflex if you’re looking for a far more affordable, better-sounding on-ear headphone than Monster’s Beats Solo HD; this is, like Incase’s Capsule, virtually the definition of what we’d call a “very good” headphone given the combination of price, sound, and design. By comparison, Sonic offers somewhat superior sound and comfort at a higher price point, plus a couple of extra frills that will appeal more to some users than others. While it’s not going to sway the typical Monster Beats Studio user away on looks alone, the price and feel are both big selling points for Incase. We’d give it very serious consideration if you’re looking for fashion-forward headphones.