As we mentioned, the most praiseworthy time to recite Shema and to pray the Amidah is as the devoted ones prayed, at vatikin. They would recite Shema slightly before netz hachamah and begin to pray the Amidah at netz hachamah. The reason for this is that normally only after the sun already shines and life and nature begin to pulsate in full force does a person awaken and recognize that Hashem is God. Only then does he accept upon himself the yoke of Heaven and is inspired to pray. However, those who pray vatikin begin early and “lead” nature. Even before the sun shines and nature reveals itself in all its beauty and splendor, they accept upon themselves the yoke of Heaven with complete faith. As soon as the sun rises and the day begins, they are already standing in prayer, ushering in an abundance of blessing to this world.
The Chachamim say that anyone who connects redemption to prayer (somech geulah l’tefillah) by praying vatikin is not harmed the whole day (Berachot 9b and Tosafot there).
However, if getting up to pray vatikin will cause a person to be tired and unable to learn or work properly, it is better that he pray afterwards. Today, when people’s lifestyles have changed and important activities such as Torah classes and weddings take place at night, most people find it better not to wake up so early and to pray after the time of vatikin.