I thought this might help someone.
We started DD on regular Similac but it caused her to scream all night long and have really painful gas. So we switched to the sensitive and it was like she just could not eat enough of it. She would down 4 ounce bottles at 2 weeks old and still act hungry. She never spit up. When we laid her down for the night, you could hear her moving all around farting really loud- like for 4 hours. Then wake up and eat and do the same thing the rest of the night.
So I switched her to emfamil gentle (DD#1 was on this with great success). The first day I already noticed decreased gas. We started a week ago and she has been sleeping 8+ hours a night ever since and she sleeps peacefully-no gas. She has really cut back the amount she eats- 3.5 ounce bottles instead of the 5 ounces we were up to.
I think a lot has to do with the bubbles. Similac had a ton of foam and emfamil does not.
Anyway, thought maybe my story might be useful to someone wondering if they should switch.