Ed was a prodigy of alchemy. Simply put, a genius.
At such a young age, his knowledge and profound insight of alchemy and of matter itself is great such that he is able to bind Al's soul to a suit of armour, even daring to attempt resurrecting his mother. Al is no slouch himself and can probably match his brother from time to time, but Ed has simply demonstrated an uncanny level in this field from a very early age.