Magic. Since magic can practically bend reality to it's will, and since it has no real limitations, then it could defeat technology anytime.
The only way Technology could possibly defeat Magic, is if there existed some kind of magic-jamming device, or if they delved into enchanted tech like Golems and such, or alchemy, and even then, that would defeat the purpose of having a war between them.
Either way, I would still side with Technology, because it's cooler than magic, and if there wasn't a war, I would become a Technomancer.