When and how to change formula brand?

Blue789

DD is currently on the regular (blue) Similac. We had 5 free cans given to us, and so far its been okay. She spits up some, but not excessively. We also have two cans of the orange Similac which we were thinking of trying. We'd also like to switch to a generic brand to save money in the future (Target or Costco). So, my questions....

1. Did anyone notice a big change going from blue to orange Similac? I know Target makes a generic of both, and we're wondering how much going to the orange would decrease spit up.....

2. Which is cheaper, Costco or Target, or using the Similac checks?

3. I've heard its recommended to start introducing the new formula rather than switching cold turkey. Advice?