The only problem with a Caddy is the cost of repair at a shop. Caddy parts tend to be a bit exclusive to Caddy. Lincoln tends to be more Ford than proprietary. As far as the car itself, they both are extremely nice vehicles. Really though, what it come down to is the car. Make a list, do some internet poking around at local places and make a list of cars to look at and go look at em. You will know when you find the car for you
And a GM 3.8 gets better mileage then what it is rated for. The 3.8 is one of the best engines i've come across as far as reliability and ease of maintenance.