True a lot of babies wouldn't tolerate multiple formulas though. My son couldn't tolerate enfamil at all which was ok with me bc I didn't like it and every other week it was being recalled. In 2012 a baby died from a recalled one and many got sick. So wish I hadn't had to go to work and could've kept breastfeeding. I haven't heard any recalls on formula lately though.
It won't be bad at all. Regular Enfamil and similac are very similar (about as different as pepsi and coke, both the same thing just slightly different) as long as baby tolerates it, go for it... If baby seems to have an issue with the change then just stick to the one.