There's no answer to that, there is no way to know in advance which particular formula will have the least short term and long term side effects in any particular baby.
Also formula composition change constantly, what is believed to be best right now may in fact be proven unsafe in the long term.
When It Has to be Formula: Optimizing the Health of Your Formula-Fed Baby
http://www.naturalfamilyonline.com/go/index.php/226/optimize-health-formula-fed-baby/
http://www.askdrsears.com/html/0/T000100.asp
Now that I’ve said that, I know some of my patients decide to bottle-feed. If you do please discuss this with your health care professional, and investigate all of the formula alternatives.
Bottle-feeding Index
How Formulas Are Made
Comparison of Formula and Breastmilk
Choosing Formulas
Soy Formula?
Follow-Up Formulas
Comparing Formulas
Lactose-Free Formula
Hypoallergenic Formula
How Much and How Often to Feed
Safe Formula-Feeding Tips
Bottlefeeding Tips
Sterilizing
Choosing Nipples
Switching from Formula to Cow's Milk
Bottlefeeding Questions of the day
http://www.breastfeeding.com/reading_room/what_should_know_formula.html
In the meantime, commercial infant formulas are not only distant in composition from human milk, but various brands of synthetic milks aren't even comparable to one another. Contrary to what the name implies, there is no fixed "formula" for commercial synthetic milk. Content and quantities of nutrients vary widely between brands and types of formula (soy, cow's milk, and meat-based). According to formula manufacturers, a pediatrician should recommend an appropriate brand and type of formula for each particular baby--advice implying that each baby's nutritional needs are unique and that physicians can recognize these special needs upon examination and select a formula accordingly. This is, of course, neither accurate nor possible.
Compositional variance between formulas persists because manufacturers must attempt to simulate a product for which they do not have the recipe - a fact FDA officials recognize in their recent statement that ". . . . the exact chemical makeup of breast milk is still unknown." As Marsha Walker notes, "Formula-fed infants depend on products which can be quite different from each other, but which are continually being found deficient in essential nutrients . . . These nutrients are then added, usually after damage has occurred in infants or overwhelming market pressure forces the issue."
Iron fortification serves as a startling example of this ongoing experimentation on infant consumers. Today's breast milk substitutes are designated as either iron-fortified or low-iron. However, William J. Klish, M.D., chairman of the American Academy of Pediatrics Committee on Nutrition (the body which recommends formula-nutrient requirements to the FDA) states: "There should not be a low-iron formula on the market for the average child because a low-iron formula is nutritionally deficient."
The Food and Drug Administration, which allows the mass marketing of low-iron formulas, states that "researchers continue to try to determine the best amount of iron for infant formula. While low iron formulas don't supply enough iron, the best amount of iron for formulas has not been established." Dr. Klish verifies that the medical community "did not have much data at the time the regulations [which are still in effect today] were written for different intake levels of iron." Studies are now underway to determine how much iron should be included in a can of infant formula. Meanwhile, commercial formulas can offer no real assurances that bottle-fed babies are receiving the proper amount of this vital nutrient. The late Dr. Derrick Jelliffe was quoted in a 1980 interview with the WALL STREET JOURNAL as saying, "Hindsight shows the story of formula production to be a succession of errors. Each stumble is dealt with and heralded as yet another breakthrough, leading to further imbalances and then more modifications."