How different are Enfamil and Similac?

Brittany

So we are going through our sample formulas and our son did really well on the Similac Pro Total Comfort.

We just tried the Enfamil Sensitive (purple canister) and after type feeds I can tell he’s gassy and uncomfortable, super fussy and he had really runny poops which is not normal for him.

I thought since they are both sensitive they had to be a little similar, is that wrong?? Are the brands pretty different?

FTM!