For some people, sure, it's faster to get to Tegel. If you arrive by car, Tegel is an awesome airport, built before airports were designed as shopping malls with a small aviation division attached, and without a strong eye towards making sure that low-paid security personnel's time wasn't wasted.

Unless you live north of Tegel though, it's going to be faster to get to either Hbf or Südkreuz, and when you get there, you just walk to the platform, wait for the train, walk on, and sit down.