The problem with DB only is that it is harder to progress with them, and actually get much stronger. Your friend probably built a pretty good base before switching to DB. You can overload the muscles more with a barbell, until which time you have build a better foundation. Plus you can still do some higher rep DB work. Most of my DB work is incline. Without a spotter on each side to load DB's I can't get enough weight on them to feel without doing a ton of reps.
My suggestions would be doing some Barbell press in something like a 3x5 or 5x5 and then do your DB work. You will build strength faster, and then be able to handle heavier weights on the DB's and will get the best of both worlds. You also get the benefit of potentiation of the muscle. After doing a heavy compound lift, the muscles and CNS are firing and it makes the isolation work easier. I also really like weighted dips, extra wide paused press, close grip press. All work the chest arms and shoulders quite well.