A lightweight road bike with rack and fender eyelets and generous tyre clearance makes an excellent commuter bike. Commuters should always have a spare bike for when one is in the workshop.
The advantage over a std hybrid bike may be marginal over 5miles but they are more fun and double up as a weekend road bike for longer rides.
I prefer long drop caliper brakes to cyclo-cross style cantilevers, they are easier to setup and have as much, if not more braking power. If you need more tyre clearance and better all-weather performance, then the disc-equipped CX style is better.