There seems to be a principle at work through much of our spiritual life. The idea that we will often get the lessor with the greater, but we will never get the greater with the lessor. This seems to be the case when we talk about surrender and obedience.
Surrender to God is more accurately understood as the giving of oneself as a gift. We give our self freely to God, as a gift as a response to the experience of God's love for us. Sometimes we can find it easier out of religious duty and obligation, to keep the rules. We might even be really zealous about the rule keeping but many report being able to do so while maintaining lordship of their own lives. This is a sure-fire recipe for self-righteousness. It is a form of godliness with no power, no genuine transformation. Obedience offers ones back but not necessarily the deepest places of who we are. Love inspired surrender gives ones whole self - including our heart - as gift to God.
Obedience doesn't guarantee surrender, but you will find, genuine surrender as a relational gift of love will naturally result in obedience. You see, you get the lessor with the greater.