with their secret arts ... Shemot 8:3
What is the qualitative difference which distinguishes the magic of Aaron and Moses from the magic of Pharaoh's court magicians? Let's consider it.
The Hebrew word בְּלָטֵיהֶם (meaning with their secret arts) derives from the shoresh (3-letter etymological root) לוט and means to cover, conceal and hide. What is hidden? Answer: the ability to retain control.
The gematria of the word בְּלָטֵיהֶם is 96, the same gematria of the word צו. Derived from the shoresh צוה meaning to command or delegate authority while retaining control, צו therefore carries the connotation of retaining control.
Taken together, it becomes clear then that the quality which distinguished the magical acts was the ability (or inability) to reveal and retain control. It may be that the court magicians' magic was produced through an uncontrolled ecstatic frenzy (resulting in unfocused weak magic), while the magic of Aaron and Moses was magic produced and more powerfully focused through remaining in authoritative control of the mind, emotions and senses (resulting in extraordinary magic).
Update / related: Knotty Control of Light