I recommend you have the dealer work up a 3 year lease which will show you GM's projected depreciation. THEN make up your mind as to lease verses purchase.
There are 2 types of lease;
1. Normal where you pay for the depreciation as you go as well as a 6.75% cost of funds.
2. SMART LEASE where you pay the qwhole amount due over 3 years up front. THEN at the end you can decide whether you want to purchase the vechicle for the projected value at lease end OR turn it in and get another one.
From what I can determine the projected residual is roughly $43k or 56% at the end of 3 years.
Consider this--IF the XLR goes the way of the Allente, the residual will be less.
In any event, you have enjoyed the car for 3 years and been able to invest the reciprical amount (47%) wisely as opposed to loosing it thru depreciation in the XLR value.
The residual is the key. If you believe it will go the way of the allante, then of course the lease is a better way to go. On the other hand, as an example, I happen to be a long term holder of automobiles. I am now selling a 10 year old Allante' and still getting $12000- back without much effort.:crazy