I have found that there is no one "best" formula, as all babies react differently.
My hospital suggested that Karicare, Nan or S26 were the better formulas - but it can really vary between each baby.
I know many people who have found that S26 constipated their babies, but others have had no problems with it.
In my experience - DD was horribly constipated on Karicare Gold. We switched to Nan HA Gold, and it has been fantastic for her.
It is sometimes just a case of trial and error to see whether a particular formula will agree with your bubs. Good luck smile