It seems that there is also a difference in BPA. I think if babies accept,
it's better to use the powder form.
Formula-feeding
Powdered formulas are the best choice for parents who want to avoid
bisphenol A in their baby's diet. While powdered formula has not been tested
for BPA, it is diluted with much more water than liquid formulas which
reduces the amount of BPA that the baby consumes in each feeding. Nestlé
has made unsubstantiated claims that they don't use any BPA to line their
powdered formula cans. Nestlé, Enfamil and Similac use a mixed metal and
cardboard package with less BPA-coating. Second best are Earth's Best
Organic and PBM's store-brand powdered formulas that use a fully metal can.
Some liquid formulas are sold in plastic, mostly polyethylene and
polypropylene which do not contain any BPA. Avoid any plastic containers
that are rigid and transparent, marked with "PC". All liquid formulas sold
in metal cans are lined with BPA-epoxy, which has been shown to leach into
the product. If you buy formula in metal cans choose the concentrated type
which is diluted with water prior to feeding. Avoid ready-to-eat formula in
metal cans, which has the highest BPA leaching potential.