Neither as both generally contain fluoride.
You should use distilled water and you should boil it. You can get a distiller or buy it in bottles.
http://www.ada.org/prof/resources/positions/statements/fluoride_infants.asp
The ADA offers these recommendations so parents, caregivers and health care professionals who are concerned have some simple and effective ways to reduce fluoride intake from reconstituted infant formula.
* Breast milk is widely acknowledged as the most complete form of nutrition for infants. The American Academy of Pediatrics recommends human milk for all infants (except for the few for whom breastfeeding is determined to be harmful).
* For infants who get most of their nutrition from formula during the first 12 months, ready-to-feed formula is preferred to help ensure that infants do not exceed the optimal amount of fluoride intake.
* If liquid concentrate or powdered infant formula is the primary source of nutrition, it can be mixed with water that is fluoride free or contains low levels of fluoride to reduce the risk of fluorosis. Examples are water that is labeled purified, demineralized, deionized, distilled or reverse osmosis filtered water. Many grocery stores sell these types of drinking water for less than $1 per gallon.
* The occasional use of water containing optimal levels of fluoride should not appreciably increase a child’s risk for fluorosis.
Parents and caregivers should consult with their pediatrician, family physician or dentist on the most appropriate water to use in their area to reconstitute infant formula. Ask your pediatrician or family physician whether water used in infant formula should be sterilized first (sterilization, however, will not remove fluoride).
Guidelines for the safe preparation of formula
http://www.who.int/foodsafety/publications/micro/pif2007/en/
3.1 Recommendations
PIF is not a sterile product and may be contaminated with pathogens that can cause serious illness. Correct
preparation and handling reduces the risk of illness.
Where available, commercially sterile ready-to-feed liquid infant formula should be used for infants at greatest
risk.
PIF is not a sterile product and can pose a risk to infants, particularly if it is prepared and handled
inappropriately. Reconstituted PIF provides an ideal environment for the growth of harmful bacteria. Even if
present in powdered formula at very low levels, inappropriate preparation and handling of feeds provides ideal
conditions for the growth of harmful bacteria, which greatly increases the risk of infection. However, the risk
can be reduced if feeds are prepared and handled correctly.
The recommendations below outline the best practice for the safe preparation, storage and handling of PIF in
the home in order to reduce the risk of infection with E. sakazakii. These recommendations are also appropriate
for reducing the risk of infection with Salmonella.
It is recommended healthcare professionals ensure that parents and caregivers are instructed in the safe
preparation, storage and handling of PIF.
[...]
3.1.2 Preparing a feed using powdered infant formula
It is best to make PIF fresh for each feed and to consume immediately, as reconstituted PIF provides ideal
conditions for the growth of harmful bacteria. The steps below outline the safest way to prepare individual
feeds of PIF in bottles or in feeding cups for immediate consumption.
1. Clean and disinfect a surface on which to prepare the feed.
2. Wash hands with soap and water, and dry using a clean cloth or a single-use napkin.
3. Boil a sufficient volume of safe water. If using an automatic kettle, wait until the kettle switches off;
otherwise make sure that the water comes to a rolling boil. Note: bottled water is not sterile and must be
boiled before use. Microwaves should never be used in the preparation of PIF as uneven heating may result
in 'hot spots' that can scald the infant's mouth.
4. Taking care to avoid scalds, pour the appropriate amount of boiled water that has been allowed to cool to
no less than 70 °C, into a cleaned and sterilized feeding cup or bottle. To achieve this temperature, the
water should be left for no more than 30 minutes after boiling.
5. To the water, add the exact amount of formula as instructed on the label. Adding more or less powder than
instructed could make infants ill.
a. If using bottles: assemble the cleaned and sterilized parts of the bottle according to the manufacturer's
instructions. Shake or swirl gently until the contents are mixed thoroughly, taking care to avoid scalds.
b. If using feeding cups: mix thoroughly by stirring with a cleaned and sterilized spoon, taking care to avoid
scalds.
6. Immediately after preparation, quickly cool feeds to feeding temperature by holding the bottle or feeding
cup under running tap water, or by placing in a container of cold or iced water. Ensure that the level of the
cooling water is below the top of the feeding cup or the lid of the bottle.
7. Dry the outside of the feeding cup or bottle with a clean or disposable cloth.
8. Because very hot water has been used to prepare the feed, it is essential that the feeding temperature is
checked before feeding in order to avoid scalding the infant's mouth. If necessary, continue cooling as
outlined in step 6.
9. Discard any feed that has not been consumed within two hours.