As Derrick says both can get boring. I would go for the turbo as it is very difficult to fall off of and doesn't have the learning curve. Get a programme together, there are loads on the market then music or videos to lessen the tedium. A couple of sessions a week to work on strength and aerobic fitness. I wouldn't do mega long sessions on it, the endurance sessions are best done on the road. Get a computer with cadence and heart rate so you can record some metrics against your sessions and you should see your improvements as you go through the winter