You kill faster with powers. No, you don't share a bar with teammates. Theirs is hidden for some reason.
I gave Vega the Chakram Launcher because despite it being heavier, he looks like he can handle it with that massive body of his. OTOH, my Shepard will have -25% power recharge if he handles that weapon before I upgrade his stat. I guess I can bring less weapon since I don't seem to use more than 2 at a time so far.
And I just realised that the big part of why I love this series are the characters. I LOVE these characters (okay, maybe not Jack or Jacob or Zaeed) and I want my Shepard to have more adventures with them.