We used CAT6. Yes it was more expensive, but in the scheme of things not such a big expense.
If doing it again, I'd probably put in more CAT6 to places where any form of AV equipment was going, as it seems just about everything comes with a network cable. I'd probably use cheaper CAT5e for light switches (we have a home automation system).
Missing out wiring a front doorbell seems common - I have two friends who both managed to do it and ended up having cheap plastic battery powered wireless doorbells stuck outside their lovely new doors. I'd actually run two cables to the door: one for the doorbell switch, and the other in case you ever want to install an intercom (possibly including a camera).
Plan for external PIR sensors, in case you want to do more than just use PIR security lights. We have a couple of places where the PIR is wired back to our home automation system, so we can do more than just have a light come on when a PIR is triggered. Ditto for possible security cameras, as mentioned above.