ARM FTW! I don't play it much now, but when I do, I'm playing as the ARM 95% of the time, with the majority of my forces being aircraft and Kbots. This is because the ARM tanks are weaker than their CORE counterparts, although if you can get some effective micro going with some spider bots, it can even the odds somewhat. I never really got into TA Spring, as my net connection is flaky at best when it comes to playing games online.
One of my fondest memories of the campaign, at least, was hitting the unit cap on the final mission by building ten or so moho metal mines, 7 or 8 of the high level power generators, an air factory, 5 advanced air factories, some base defences, an advanced radar and the rest was filled with Brawlers. Lots and lots of brawlers. Enough to wipe the entire map clean in one fell swoop.