Leasing Pros:
a) It's easy
You don't keep any equity in the car
Don't have to deal with dealers, so no playing games with what's my car worth, how much can I get off etc
Costs are known up front
Leasing Cons
a) it is generally the most expensive way to fund a vehicle
b) You cannot easily get out of the car half way through
c) Options make it very expensive very fast
d) You are charged for damage
e) You are charged for extra mileage so it can develop a 'dont want to put miles on car OMGZZZ' mentality, in which case why bother having a car if you are scared to use it?
Buying Pros:
a) It's almost always the cheapest way
b) You own a car you can sell if needs be whenever you want to or keep for as long as you want
c) You have complete flexibility over the car. New, used, approved used, nearly new, whatever spec you want, no problem
d) Damage it? Your car, your problem, do what you want
Cons:
a) It requires you to have the money, or borrow the money
b) It exposes you to unexpected market shocks, ie bottom drops out of market
c) Sometimes you miss a deal that's only available via a lease