Baby formula Similac vs Enfamil?

My mom has been talking about what formula is better for my lil brother. We get WIC and they give us Similac free but my mom feels like Enfamil is better but she cant realy back that up with evidence. i told my mom id do some research and ive read up on ppls pref and most everyone says ther all the same... wel yes but if you take it down to the ingedance of both i wonder is somthing perticularly needed for somthing my brother is lacking and could be better for him at certian times... im curious and wondering if somone has realy nailed down on the details. my mom gets Enfamil with coupons and mixes it half and half with Similac my brother doesnt seem to mind either but still we would like to know what makes the difference... i kinda want more then they are basicaly the same but any help would be greatly apresiated. :)