I hope I don't come off as a dick, but I was definitely you at 16.
I'm 27 with a college degree and a full time job in IT and I could barely afford a WRX. I find it hard to believe you are able to buy one either. Obviously, I don't know you or your financial situation but I would caution you to avoid biting off more than you can chew at your age. Besides the cost of the car you have to worry about a lot of hidden costs in buying a sports car. Especially an AWD turbocharged sports car. In a WRX/STI you have to use premium gas - which at first isn't a big deal until you realize that if you also have to try pretty hard to keep it in the ~20mpg range. Also, if you blow out a tire, you can't just replace one, you have to replace all four. If one tire has significantly more tread, your drivetrain will suffer. If you have any sense you'll want to use high quality, full-synthetic oil, and change it quite frequently, and other stuff I can't think of at the moment. My point is just because you can afford the car payment doesn't mean you can necessarily afford the car.
I've been in your situation. I've wanted a Subaru since I was 10, and it took me until last year to be confident enough in my financial situation to afford my WRX. I know what you're thinking now, "I will get a used one!" I did that too and ended up having to pay thousands to have the engine rebuilt after I found out the previous owner had abused it nearly to death. I'm definitely not trying to scare you away from the platform, just make sure you think long and hard before you throw your money on the table. Have you considered just a regular Impreza? I know you've got the turbo-lust but perhaps an Impreza would get you familiar with the chassis, handling of the AWD, etc. Then, when you've got even more money saved up you can trade in a car that has excellent re-sale value for your coveted WRX/STI.
Now for the fun part:
Lets assume you do have ~$25-30,000 laying around in unmarked non-sequential bills burning a hole in your pocket. You now have to decide what the car is for. It sounds like it's going to be a daily driver. My deciding factor was cost, but if yours isn't, hell get the STI. The STI has a a more aggressive engine, better brakes, a controllable center differential, etc. If you want a track/rally car - this is your best option. But honestly, do you need those things to have a fun daily driver? Nope. If you're only going to do a track day once a year it probably isn't worth it. Also, try not to lend too much credence to the "well the WRX will still beat a STI 0-60" that you may hear WRX guys shouting - I would still take an STI for a track car. It has all the little things you want in a race car that you would find yourself going to the aftermarket to get for a WRX.
The other part you have to think about is the social aspect. I didn't consider this AT ALL before I bought my WRX. The first thing I want to say is the Subaru community is the best. I've owned BMWs, Hondas, a Jeep, etc. and nothing compares. Other WRX/STI drivers will wave to you when they pass you in traffic and park next to you if they see you in a parking lot. There's a lot of enthusiasm and love in the Subaru scene and I hope to welcome you to it but there is also a "boy-racer" stereotype you will find others on the road act on. Especially with an STI (with the big, recognizable wing) you're going to have people being jealous/butthurt and not letting you merge in to traffic or back out of a parking space. Everyone will assume you vape, wear flat-brimmed hats, and drink rotella out of gallon jugs. You will have a constant onslaught of kids with fart cans on their Honda Civics and Dodge Darts revving at you at stop lights and on the highway. The muscle guys with Camaros and Mustangs will either roll their eyes or make "lesbian limousine" or "ricer" jokes at gas stations and car meets despite your car being completely stock. I've even witnessed a group of 3 teenage girls sitting on the hood of my car to take selfies, unaware of my existence until I approached with my cart of groceries and told them to get off my car. People see the hood scoop and, on the STI the spoiler, and think "OMG IT'S FAST AND FURIOUS!"
My point is these cars get attention. Enjoyable car-enthusiast attention and also non-enjoyable police/idiot attention. For a while the WRX was the most ticketed car in America. There is a level of maturity required to deal with this, that I doubt I had at 16. Again, I don't know you, maybe you do. If you're going to get heated and try to race random people revving at you or be offended at the muscle-car-guy jokes you need to re-evaluate why you're buying a sports car.
If I were you, I would do what I did. Buy a $2,000 used beater that you don't need to worry about denting or breaking in a few years. This will at least get you out of high school and saving money, instead of worrying about a car payment. Again, I can't recommend an Impreza enough. If you plan to go to college the hatch would be a great choice as well. No matter what, get professional instruction, hit a few track days and make sure you've confident in your driving abilities before you buy any kind of sports car.
At any rate, no matter what you choose to do, I'm just happy you're interested in Subarus and I wish you luck with whatever you decide is best!