Ok, here's the thing.
If you buy a car, how much money are you going to put down? If you are putting little to none, you are going to be looking at a financed amount of about $28,000(after TTL). At 60 months loan, at 6.9% interest, your loan payments are wee bit above $550. After 36 months of payments, your payoff is right around $12,300.
Judgeing by Edmunds resale ratings on a 3 year old GT Eclipse Convertable, trade ins are anywhere from $8,000 to $11,000. That's a complete estimate there. Assuming you landed in the middle of that range, you'd still be $2,000 or so upside down on your trade in since you still owe over $12,000 on the car.
If you plan on trading in your car after 3 years, or less, then you will still owe a pretty good chunk of $$ on your car, just to get an even trade in.
Check with a Mitsubishi dealer and see what lease payments are running on the specific car you want. You then need to compare two things -
1. monthly payment and how much you are willing to pay
2. how long you intend on keeping the car - THIS IS THE KEY thing you need to consider. If you KNOW that you are going to want to trade up in three years time, and you aren't making a big downpayment, then you would BE FOOLISH not to lease IMHO.