Just whatever you think you'll enjoy. Don't worry too much about practicality.
If you want to go fast, a road bike. If you want drop bars but still want grassy/gravel offroad capability, a CX bike.
If you want to go offroad, get a mountain bike.
Generally though, if you're not going to leave the roads then get a road bike. A CX bike if you still want the option of leaving roads but really you'll rarely ever do it. Or if it gets really cold with shit roads and you need studded tires. Tire clearance is needed for ice tires.
