Help! Which formula is lightest on tummy / best?

Bee
Any thoughts on the differences between the formulas? I know they all have strict regulations but wondering if there are nutritional differences? 
Also what formula seems to be scientifically lighter on the tummies?
I am supplementing currently with Similac total comfort. Previously used Nan 1 as well. No real issues although only started on similac TC on Friday and since then my boy is showing signs of colic / silent reflux (going to docs on Friday). However he's 4 weeks so the age where only this would start showing so not sure if it's anything to do with formula?
Thanks for any help you can give me! 

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