Omnis: Keep in mind that your opinion of the M45 is just that, an opinion. There are going to be plenty of people who love the car (like you) and dont care much for the car (like GT4_Rule).
Let me explain my reasoning for calling the two a tie:
Although both cars are designed and built to compete in the same class, both take very different approaches to the way the car was designed both on the outside, and mechanically speaking.
-Cadillac STS: The styling of the car follows the in-house design theme "art and science" that has been changing the brand since the late 1990s. Although it has not been widely accepted by everyone, I think it is safe to say that it is a pretty good looking car by days end, and gets its point across. The car was not meant to be as sexy as the M45, much more utilitarian similar to the designs that have been on the German models (of which Cadillac has made it's primary targets) of the past few years. Cadillac kept in mind that older folks are still going to be buying Cadillacs, but at the same time they wanted to attract younger people that often flock to Lexus and BMW for their new ride. They made a compromise, struck a balance, and came out great in the end.
-Infiniti M45: This is a sexy car, and it does a great job of following Infiniti's new obsession with making everything look like a sportscar. The lines and porportions are just right, the look is very clean, and is very daring when compared to the Caddy, BMW, and Mercedes offerings. I would dare to say that only the new Lexus GS compares in outrageously good looks, but these designs are meant to appeal to younger people looking for a nice ride.
- Conclusion: I gave the two a tie because they focus in on their respective target markets while competing in the same class, and thus they must be reguarded almost as completely different types of cars. The STS does a great job of finding a good balance between the new-age Cadillac and the Cadillac your Grandparents grew up with. On the other hand, the new M45 completely outclasses it's predecessor, and ups the ante in the design game, but almost too much. If the Cadillac is too boring, the M45 is too outrageous, and thus they cancel eachother out in terms of design. As sid the Sloth would say, "They complete eachother."
As far as price and performance goes, it is also a matter of what model you are refering to, and what market you are talking about. At $60K, you can check every option box with the M45 Sport, but fully optioning an STS Premium Luxury Sport will run you just shy of $64,000. Performance differences are somewhat slim, but keep in mind that both cars are designed for different types of buyers in the same category.
If I had the cash, I'd probably end up with the Cadillac. Mechanically speaking, it will last longer (the Infiniti 4.5L V8 has been known to have head and other oil problems in the past), and would be vastly more comfortable when just driving around town. The resale value may not be as great as what can be matched with the Infiniti, but, who cares? The Caddy fits my tastes much better than the M45, but it might not with others... Again, its just my opinion.
Also, IMO, QX56 is the only "crap" in the Infiniti lineup.
