For business purposes, when you lease a vehicle, you get to right off the cost immediately (spend $4000/yr, your writeoff is $4000/yr). If you buy a vehicle for business, you can writeoff the maintenance expenses or take mileage, but you can only depreciate the vehicle. For example, you might spend $6000/yr on payments, but can only depreciate $3500 that year. SUVs and heavy trucks get special treatment with regards to depreciation.
For personal use only, there are no tax advantages for leasing or buying outright.
I don't think leasing is financially smart, but can be good for other reasons.
Some guys will buy off-lease company cars. I suspect the buy-out price is good perhaps because the employer pays a high monthly lease price (good writeoff). Note the market is flooded with tons of off-lease cars selling at bargain basement prices, so I'd imagine the prices are very low. All pure speculation on my part.
If you know what you want, buy a clean off-lease car. I bet the monthly payments would be far less than leasing a new model, and you'd own a car that has already taken a huge depreciation hit. Of course I have been accused of being a cheap b@st@rd.
Jürgen