I would also recommend asking your pediatrician.
We had to move to formula when our daughter was 10 weeks old so I could start chemo. We asked the pediatrician - his opinion was that you should stay away from soy unless directed by your doctor. As far as brands, he said he could verify all the scientific claims made by the big names (Similac, Enfamil, etc - he wasn't so keen on Nestle Good Start, but I don't recall the reason).
Though other formulas may have the same ingredients, they may not be in the same proportions, so he couldn't substantiate any claims they make. We ended-up using Costco's Kirkland brand for most of our daughter's first year. She was always above the 90% in height and off the chart in weight, so we think it did OK.
Every child will react differently to different brands, so you may need to get small quantities of a few (or ask your pediatrician if they have samples of a few different ones you can have on hand for that emergency).
Good luck with your return to work!