Let me put it this way. The CX 3.00 sounds really..."unspecial." in fact, the CX 1.00 2.00 3.00 5.00 all have this issue. They might have a fair amount of bass, but the sound is oddly un-distinctive. They're not bad at all, but as an example, Sennheiser's own Momentum IE is tuned to sound way sexier than the CX 5.00.
Anyone who wants a Sennheiser IEM, I'd say just spend extra and get the Momentum IE, it's really that good.
The EX650 has a lot of bass and pretty intense treble, so here the question is reversed - is that excitement too much for you? If you're after excitement then it's an excellent pick.
Don't count on either one being more durable than the other.
Having said all this I'm not sure how I'd vote. Probably Sony, but the EX650 is too intense for my tastes, so I'd downgrade to the EX450.