If you are already using React for the web (which I would believe is the biggest reason to use React Native), then the RN layer is pretty much already taken car

If you are already using React for the web (which I would believe is the biggest reason to use React Native), then the RN layer is pretty much already taken care of in term of expertise. For the iOS and Android side, that's a constant between the two possibilities. It's better because now your iOS and Android experts can concentrate much more on what they do best and your React experts can keep working on your UI like they always did.