The main advantage of using Yearn over Convex to stake CRV is that Yearn offers auto-compounding rewards. This means that users will automatically receive their rewards each time they stake their CRV, allowing them to maximize their earnings with minimal effort. Additionally, Yearn is currently offering bonus rewards to those who stake their CRV through styCRV, which provides an additional incentive for users to use the Yearn platform. By using Yearn to stake CRV, users can take advantage of the auto-compounding rewards and bonus rewards, allowing them to maximize their earnings with minimal effort.