Too much info for me to remember at one time. It costs the same overall and I know the info I need for the first half. Access-lists I have heard are a bear on the test and I would rather be able to focus more study time on them than wonder what is going to be on the combined.
I have talked to a bud in ATL who works with a bunch of Networking people, he mentioned that people tended to be in favor of splitting it up because of the amount of info you have to test for. I don't get to use the info day to day so I'm trying to maximize the possibility of passing. I feel confident in working on routers and switches, just not a great test taker.