IMHO post burn-in the bass level is about the same but more refined with the e2c.
IMHO part of the reason the sony EX sounds so bass heavy is because the mids are severely recessed.... so the spectral balance is all off.
For the price range the E2s are the best way to go for bass response. That's a big selling point for me, and the E2s are the only canal phones that i've been impressed/pleased with. If you can find one of the deals, where they're selling them for $70 or so, they're a good deal. And Shure has a good warrenty on them, so if anything should go wrong with them, it can be dealt with.