Ken,

I've done both in the past and finally ended up having my company purchase two of my cars from me. I really despise keeping mileage logs and some of the other paperwork required to pass an audit. By having the company purchase the cars I don't have to worry (personally) about some of the issues that arise when you use a personal car for work.

As long as you remember to drive your "personal car" when out for theater and drinks Friday night all is good. Hit someone in your "work" car while out socially and you have issues, either way you're screwed it's just a matter of how hard.

It's amazing how complex these issues can get and how much money is spent on understanding them.

Matthew