Can't say much about KE30's because I've never driven one, but I own a KE70 so here's my 2 cents.
They're not as old as '30's so parts are a lot easier to find. Both have 4K engines but I think the KE30 is lighter, so it might be a fraction quicker. Probably only by a bee's dick so let's just say they're the same in that respect.
KE70's are popular platforms for race/drift applications because they have a strong chassis, there's loads of aftermarket/interchangeable parts, and here on Rollaclub there's tonnes upon tonnes of support for things like 4A-GE engine conversions, suspension upgrades, and so forth. Lots of bits pretty much bolt straight into a KE70 for upgraded performance (even KE30 lower control arms for negative camber), whereas with KE30's you might find yourself running into situations where you'll actually have to fabricate mounts, crossmembers, etc. or modifying existing hardware to make stuff fit.
Then again, the older the Corolla, the cooler you'll be... :elvis: