Corporate leasing permits the corporation to directly deduct the yearly cost of the vehicle (lease payments, gas, maintenance, etc.). A corporate purchased vehicle is depreciated over time, and you also can deduct the gas and expenses. Now, if your company buys a large truck (over ~6000 lb GVW), you can accelerate the depreciation.
There's also a difference when you get rid of the vehicle. When you trade in your lease, you tax liability is zero. If you sell a purchased vehicle, you have to pay depreciation recapture. So, if you plan to keep the vehicle for a long time, purchasing might be best, but if you plan to keep the vehicle for a short time, leasing might be optimum.
FWIW, I am NOT a tax expert. You should verify everything I say, and when in doubt assume I am 100% incorrect.
