There is no "proof". There aren't crash stats on seats when they are actually in use in consumers cars, so it's not something that can be followed. All you can do is read user reviews and car seat tech's opinions. Techs undergo training and then continuing education. Many take their certification VERY seriously and though it's just an opinion, their opinion is based on their experience and knowledge of how things works. However, that's basically as good as it is going to get.
I can tell you that the SnugRide is DEFINITELY not a great seat. In the US, car seat companies choose a price that mass consumers are comfortable paying and then build their seat around that price. It's sad, but true. You aren't getting the best possible seat when it is built on a price. Sure, it will pass all the minimum safety tests for approval and may be the best in it's price point, but you can do better sometimes. I also don't think Britax's infant seat is anything to rave about. They have been big in the convertible and toddler business for a long time. When they sold their company it became a numbers game. It's just about how much money they can bring it and how fast they can do it to sell the company again. I think their original products are GREAT, but the newer ones in my opinion they skimp on and ride on their name. From my research I loved the Orbit seat, but for the Orbit system. My next favorites are the Cybex Aton, Chicco Keyfit and from what I have seen I like the Maxi Cosi Prezi but I'm interested to see more reviews over time on it.