I used to do a 25 mile commute on either a CX with slicks or a road bike – the CX was about 10 mins slower over the distance but it did give me the option of canal towpath routes etc.
Personally I'd go for a CX and either 2 sets of wheels or just be prepared to do a fair bit of tyre swapping! Great bikes, SO versatile. I did the Fred Whitton Challenge on mine (with slicks) and it was fine, kept up in the bunch but the lower gearing allowed me to ride Hardknott and Wrynose Pass. 🙂
It's survived the Three Peaks CX as well.
Forces you to relearn technique as well – sliding round in the winter mud on 1.2" tyres at 90psi is a great laugh.