Armour vs Synthroid

Today I finally got my bfp after 5 years of trying. Now my doctor tells me she wants to switch me to synthroid from Armour. I don't want too. I feel so bad on it. I don't think now is the time for her to mess with my hormones if Armour is working. Anyone here taken Armour during pregnancy? Or can give me any sort of insight on why one is better than the other during pregnancy?