From the 2 you mentioned I would pick Female Sniper for the 2 of the 3 reasons you mentioned:
1. How fast you can get to 50 depends if you use legacy perks, cartel experience bonuses and how regularly you'll play with that toon. I'd recommend buying legacy class quest, flashpoints and warzone perks (I'd would only take you a day of dailys with 2 of you 50s). That's up to you
2. Voice Acting: Jo Wyatt voice acting blows my bind, from my opinion she does very good with her voice to express emotions.
3. Story: This is where IA excels, you can have so many different situations whether you're Dark, Light, Neutral, Pro-Sith, Sith hater. And the story get so many twists through it. For me it's like the story telling of ME and DA.