Name Brand vs. Store Brand Infant Formula: Is there a difference?

This is a guest post written by my sister Catherine.  She recently had twins and has been buying formula like crazy to keep up with them.  This article is about her research involving name brand formula versus store brand.  She is also a pharmacist and mother of 3. 

 
With the twins' increased nutritional needs as they grow, their formula supplementation has increased and they are eating us out of house and home!  (With brand name formula, anyway.)  We intially used brand name Similac Advance we had stockpiled before their birth when CVS had 30% off employee discount days, combined with $5 manufacturer rebate checks on each can.  That wasn't bad.  Then we were getting it at the regular 20% off emp discount (which basically made it the same price as Wal-Mart & other big discount retailers, but CVS was just more convenient since Matt was already there) + rebate checks.  Alas, we ran out of rebate checks last week.  I then bought a big container of Similac for $21 at Wal-Mart, which only lasted about 3&1/2 days since we are feeding 2 babies 6 oz bottles every few hours.  The next time, I ran out in a formula emergency to the closest grocery store to our house, HEB (a TX chain).  I noticed they had a store brand of the Similac Advance for $11.88 for the large can vs $21 for the same size of the brand name, a greater than 40% savings.  I broke down and bought one can of the generic to try out.  (I had never used generic on any of my kids before)  I found that it mixes well, the twins eat it with the same vigor as the name brand, and, in fact, their stools are more regular with the generic!  This morning I went back to HEB and bought 3 more large cans to get us through the next several days, including our trip to Naples, FL this week.  I didn't want to run out there since I don't think they have HEB.  Which got me thinking and researching...
 
Q:  Does the same company that makes the HEB formula make other store brands in case I can't make it there?  (One of the reasons I had always had a brand allegiance to Similac was that I could find it at any retailer that sold formula and know that my baby was being fed the same thing.  I didn't want to introduce something new constantly, and chance gas, fussiness, etc...)

A:  Yes!  I called the 800 # on the back of my formula can, which rang PBM Products, a USA company.  I spoke to a rep and found out they make pretty much all of the store brand formula.  (And it recently won another huge lawsuit against Mead Johnson, the maker of Enfamil, who had deceived customers into thinking that its product was somehow nutritionally superior to the store brand.) 
 
Q:  Were there any additional coupons that could help me save even more on the store brand?

A:  Yes, I filled out an online form which will supposedly give me a $3 off coupon and I think I can call and request it monthly.  (And I read on one blog that I may be able to get 2/month since I have twins.)
 
Here are some links where I got my info:
 
http://iamwickedcheap.com/2010/08/05/free-sample-parents-choice-walmart-brand-infant-formula/
 
http://www.pbmproducts.com/default.aspx
 
http://www.storebrandformula.com/default.aspx
 
Maybe you already knew all of this, but I found it to be eye-opening and exciting.  I am hoping to largely use store brand formula from here on out till the twins are on milk.  It shoud save us a ton of money!