Babies are often gassy. My 11 month old LO sometimes farts like an adult.
I'm certain that at 11 months your girls eat many different things. Each and every one of those could make them gassy. Try to skip the formula for a few days, just feed them normally and give them water or watered juice. They will, most likely, still be gassy.
Asking about particular products is not a good idea. Mostly because all children are different - and they react to formulas differently. Whatever specific answer you get here will be subjective and may not apply to your little ones.
You can try different formulas yourself. Check which one the girls like best, which, perhaps, make them less gassy. A week or two with each should be enough to get a general idea how each works.