This is a very unfair question because there are a great many people out there that are stuck in the past and think that Colts are the "end all" when it comes to 1911s because they were the first. So, I guess Fords are the best cars since they were first, huh? If truth be known, I'll bet that over 75% of these Colt lovers have never shot much less, owned an STI. So how can this question be fair?
I remember the first time I shot an STI. It excited me and I said "I've got to get one of these!" And I did... a few days later I bought a Spartan. I took it to the range and Boy was I disappointed. Sold that gun and bought a Trojan. AHHHH! The difference between a Spartan and Trojan are astranomical. There it is! I loved this gun. My gunsmith does the most incredible trigger jobs I've ever felt so the only thing that I've done to it.
All of this while owning a Gold Cup which I IMMEDIATELY sold.
STI guns have a feel thats all their own. It is different and I love it. I am going to buy another STI very soon, I just haven't figured out which model. I will never own another Colt unless it's a Singer or Union Switch & Signal .... oops they're not Colts either!
I don't see why it is an unfair question. It is always a matter of perspective. A lot really comes down to aesthetics because most people even here on this board are not going to outshoot either of these pistols. If you bothered to read other people's post in this thread you would see that most people commenting in this thread own/owned or at least have shot STI guns enough to form an opinion so your made up 75% figure was factually inaccurate from the moment you posted it.
Your car analogy is also a huge fail... Ford did not invent the car. IIRC Benz Patent Motor Car was first. Cir 1885. People don't love Colts just because of the name. They love Colts because for the most part they have made good guns and they hold their value better than any other production 1911. If you buy smart you can literally buy a Colt shoot a few thousand rounds and sell it for every penny you have in it. Can't say that about many brands of 1911s. So it is not rooted in fanboydom it is rooted in their place in the market.
I personally if I had to choose between these 2 guns I would get a 2015 Colt Gold Cup with a 70 series ignition. It is not that I am stuck in the past. I am firmly rooted in the present and despite Colts current financial issues they are producing some of the best guns they ever have. Their newer equipment is allowing them to compete a little better on price while keeping quality high. They are better than the guns from the 80's and 90's when Colt machinery was past its prime. They are making good guns and there is a reason that top smiths like Yost, Burton, Williams, Harrision, Garthwaite etc... like to use them for base guns.
Now the STI is a good gun. They are simply not my cup of tea. I am not a fan of the front serrations on the slide. I don't like their giant STI billboard of a logo although they have toned that down quite a bit in reason years. I am also not a fan of the skeleton trigger or the front strap and mainspring housing texturing. I prefer classic checkering to the chainlink looks.
The guns shoot and I understand why people like them but they simply do not float my boat and there are many other 1911s in that price point which do so why would I choose a STI? Does not make them bad just makes them not for me. I do not find them aesthetically pleasing and in the hand they do not feel any different then other single stack 1911s. Everything I do not care for about them are some of the same reasons people love them. I am glad there are lot of choices in the 1911 market place and do not have to settle for something we don't really want. I have not found their out of the box triggers to be significantly better than other 1911s in their price range and clear either did you because you took your Trojan and had a trigger job done on it.
In the end you like STI guns. That is great others don't. Does not make you right does not make you wrong. I guess I don't understand why people feel the need to bash one product in order to justify their like of another competing product.
To the OP get the one you like best. In the end both will most likely serve you well. As I have pointed out the main differences will be aesthetics and subjective personal preferences not objective differences which will show up on the range. IMHO