I have over a year of hanging experience (I started a while back and had to stop, then restarted recently), and I have only hung BTC and SD. My advice when it comes to hanging is this: DO WHAT IS MOST COMFORTABLE. BTC and SD, as DLD said, both basically target the ligaments, so it really doesn't matter too much which one you do. The important thing is that you go with one of two approaches, either do a minimum of ten hours a week or else focus on hardcore hanging, but either way you need to focus on your own comfort. If you want to do the ten hours a week it is best to be comfortable because that is a lot of time. What I personally do is lay down flat on my bed and hang the weight SD over the edge of the bed. If you instead want to do hardcore hanging, which is heavy weights for only one or two 20 minute sets a day, you still need to find what is most comfortable.
If you aren't feeling too much stretch in your ligs, it could either be because you aren't using enough weight to feel the stretch or your penis is personally tougher and able to handle more weight than the average guy. In either case, just because you only feel skin stretch this doesn't mean you aren't gaining, because you very well could be.
IMO, choose either SD or BTC, whichever is most comfortable, then continue to do that until you go at least 3 months with no gains. When that happens transition to hanging over the shoulder, OTS, or any other higher angle to target the tunica more. Generally, depending on your penis, you should be hanging BTC or SD for a good amount of time, like a minimum of a year. That doesn't mean that you should do it even if you see no gains, but generally most people need to stick to it for that long.
