I looked into auto transport years ago when I bought a used E46 M3 cab from a guy in Wisconsin. The horror stories caused me to fly out and drive it back. I agree that enclosed is best but obviously more expensive and then I believe there is even a pricier option of single car transport.
What scared me is the fact that many companies use independent sub-contractors (basically just guys who own or have their own truck so in many cases little is know about the guy in charge of your car, his professionalism and reliability included. Also they usually pick up a bunch of cars to fill their load so they drive all around and can take a very long time to get to you. You'll find that these companies will only give you very vague estimates of when your car will arrive.
Finally, I've read that, depending on the order of delivery, your car may have to be driven off and back on the truck a number of times by this driver. I shudder to think! Maybe I'm paranoid and just remember the stories that scared me but if I was in your shoes I'd want to know the down side. Good luck