Take the allowance, with so much conjecture in our jobs, you might have a job one day and gone the next. I like the fact that it's actually my car and not something I'll lose if I lose my job.
Thats great except that you generally buy an allowance car on finance and then you must rely on finding another job that offers an allowance. Thats if you can find a job at all atm. With a CC if you lose your job, you lose your car but at least you don't have a debt commitment to worry about.
If you buy a car on allowance, you also take the hit of depreciation that comes with it, plus you have to ride the petrol prices and cop the Insurance premium if some dipsh!t runs into you even though you are out working. In most cases, you also miss out on fleet discount when you buy the damn thing. Its also sh!t house if you have a car on finance with your allowance and you are looking for finance to buy a home as the car debt still counts towards your borrowing ability.
CC all covered by the company, no exposure for you except for the fact that you lose your car should you lose your job. In most cases, a lot of companies will let you continue to use your company car for a couple of weeks if they make you redundant anyway.