Magic and tech are indeed balanced. The only problem I've ever had is the fact that the cpu creates magic units way earlier than it does tech units. The result is tech usually getting destroyed in the beginning of the game.
Magic is the faction for me. I've held off 2 cpu ultras with the magic faction. If you're concerned with the fact that magic has the potential to kill your own units because of the splash radius then magic is not for you. You won't kill your own units if you choose the right combination of units to send to battle. For instance, if you send 10 behemoths and 10 archmages to battle then the behemoths will most likely not survive and it would be a waste seeing as how it takes some time to create a behemoth. If you, however, combined dragons with archmages, then that's a powerful strategy. Personally, I always have a group of archmages I like to call the "suicide squad". One time, the cpu ultra managed to gather 60+ units against me. You can't beat 60+ units with tech. However, if you're using magic, just create about 10 archmages and get them to use their flare attack (the one that costs 1000ep) all at once. People say the flare attack is bad because it costs so much EP and it KILLS. I say different; I love the flare attack because I could MURDER A LOT OF UNITS.
One more thing that magic has is a better experience system. Tech units only have 2 experience levels (normal and elite). Magic units, however, can unleash all sorts of hell. Have any of you ever seen a "legendary" archmage unit. IT'S A GOD. When used correctly, this one unit can destroy so much. Sometimes, when I really want a legendary archmage, I will summon a lot of daemons and slaughter them with the archmage. Another useful unit is the drake rider. At first they're not that good, but when they become "master" drake riders, they have so much defense and are useful in the battle field. Their very usefull for "hit and run" and scout tactics.
Forgive me for writing an essay, but I fully believe that tech is for beginners and magic is for the experts. Tech may give you a quick victory, but If you want BLOW THINGS UP, use magic. It's much easier to defeat the cpu ultra with magic than it is with tech.