This has been an interesting thread. Thought I'd toss in my .02 worth (which is about what it's worth-LOL).
Oddly enough, I happen to own an example of all three of the cars being discussed. My Imperial is a '65 Crown convertible, my Cadillac(one of them) is a '66 Eldorado (convertible) and my Lincoln is a '70 Continental Mark III. I happen to be very fond of all three for different reasons. They are all very powerful but the fastest off the line is, hands down, the '66 Eldorado. It has a 429 under the hood that is only slightly larger than the Imperial's 413. I've been told it is the switch pitch transmission that seems to give it the edge over the other two. It has so much torque it will throw you against the seat if you step on the gas too hard! I've had the Imperial's engine rebuilt to the specs. of the '65 300L and have even gotten a 300L carb. so I'm hoping those 5,345 lbs. will move away from a dead stop a lot quicker once the car is totally finished.
>From a styling standpoint, the Imperial is probably the most unusual whereas the Cadillac and Lincoln are both rather understated. Cadillac was very careful not to drift too far from the traditional Cadillac look with the egg crate grille and vertical taillights. Of course, the headlights are stacked rather than horizontal but there is no mistaking it is a Cadillac whether sitting still or driving down the road. The '66 Eldorado is the last rear wheel drive Eldorado ever built as well as the last Eldorado convertible from the Sixties so it has some history that goes along with it. I first saw Imperials on The Beverly Hillbillies T.V. show and when I started collecting cars from my youth in the early nineties, the '65 Imperial was in the top ten on my list. As far as engineering goes, I agree, the Imperial is a true heavyweight. For example, the drive shaft has two sections as contrasted to the one piece drive shafts on the other two cars. Every aspect of the Imperial is 'over the top' in design and construction. It has been undergoing a frame-off restoration (for way too long now) so I know each and every part of the car. Nothing is flimsy. Even the glove box door weighs a ton!
The Mark III is an elegant car that is also very powerful (460 cid) and extremely comfortable. It is a pleasure to drive and really turns heads with that 'spare tire hump' in the trunk. The front grille is a masterpiece of design.
As for my love of the three, I have no real preference. I am crazy about all of them! I wouldn't say I preferred one over the other. I just enjoy them for their own merits. It's like having three children. You don't love one more than the other. You just take care of them all and appreciate each one for its own special qualities (and quirks)!
Greg McDonnell
(no brand loyalty)