Poll of a sort: treadmill or bike trainer?

Ladyslippers

I spent the warmer months walking for exercise, with trips to the gym for weights. The gym is not convenient to my house (so once my contract is up I have to decide whether to stay (I DO love my gym) or find one closer to home until the new building at work opens up with its new gym inside.

ANYway, I've been wanting to start biking, for exercise and so that I could go on family bike trips with my boys, but didn't get around to looking at bikes before the colder/darker weather set in. My older son outgrew his bike, and I'm thinking it'll fit me just fine, so I thought of getting a bicycle trainer and riding his bike in the house for indoor exercise in the winter.

But then a friend let me know that she's selling her Nordic Trac treadmill. It's in great working condition.

The prices are comparable. Floor footprints are comparable. Treadmill takes up more square footage and isn't as convenient to store (I could hang a hook in the garage ceiling for the trainer). But I've been committed to walking and walk/jogging and know I want to keep up with that, maybe with bicycling on the side. I can't afford both and I am having the worst time deciding between the two.

Any words of wisdom or anecdotes? Thanks!