First, YAY! ask box question of awesome!! THANK YOU!
Now, moving on: Hmmm, this is an interesting question, keeping it to female heroes I want to say Batgirl (Steph) or Batwoman (Kate Kane) because they are both super AWESOME, but I don’t think I could, nor would I want to, put up with Bruce “holier than thou” Wayne.
Being Big Barda would be awesome as would being Ice (BEFORE Winick got his hands on her).
I think though, that it would come down to Artemis and Kate Spencer (Manhunter) for me and I would really be hard pressed to decide for certain between the two.
If I could be a male hero I would, hands down, without a doubt, be Guy Gardner.
Villains - probably would like to be Earth 3 Super Woman or Harley Quinn (although I would be all about Riddler rather than Joker). Male side Riddler or Bane.