If we discovered magic today, we wouldn't need to discover cold fusion or mass reaction, we'd just use magic to fill in the unobtanium blanks in our current warp drive theoretical designs and sail to the stars right away.
If we had discovered magic before the LHC, we wouldn't have needed to discover the Higgs' boson, we'd have created it.
If we had discovered magic before Einstein, we wouldn't have needed to discover the relativity theory since we already would have magic portals.
If we had discovered magic before the steam engine, we wouldn't have automobiles now, we'd all ride magic chariots and brooms and cat buses.
If we had discovered magic before laser, we'd all be making war with deathray-spewing magic wands.
If the first homo sapiens had been born with magic, we'd have never needed to discover the wheel.
Invention is the product of need. If the satisfactors already exist, there's little need for less efficient alternatives. It's not "either magic OR science," in fantasy worlds, magic is their science.
A world with magic wouldn't evolve into us, it would evolve into some magical post-scarcity society with crystal ball-based psionic internet and Shakespeare theatrical troupes with Hollywood-grade FX. Something like Dalaran or Dragon Half or whatever fantasy anime. What you can't keep from changing and evolving, though, is society. Sooner or later people will demand equality and not living in the muck, and sooner or later, some industrialist mage will do "The Great Leap Forward" in fantasyland.
...and an imprisoned god in the city hall's sub basemen)
