A good idea might be to try a mixture of both - a little bit of barefoot running on the treadmill combined with some running outside in your KSO's. If you're just getting into barefoot running, you want to be really cautious about overdoing it. Your feet and lower legs need time to strengthen and recover, so it's best to run barefoot or in VFF's only 2-3 times per week to start.
It's harder in the cold, so you may need to start by wearing VFF's and then make the transition to totally barefoot in the spring when it's warmer.
Cheers,
- Fitz.
www.strengthrunning.com