This may be abit "unhelpful" lol as i have changed FROM Aptimal comfort TO Aptimal 1st milk...my LO was on aptimal comfort for constipation as it was supposed to help his stolls softern a bit well lets just say it did it's job! lol it does take some time getting used too becuase at first it made his poos very runny and green tehn after a few days it went to it's usual mustardy colour Sorry tmi..but the reason i changed to aptimal first was it seemed to go straight through him! and seemed to be more like a laxitive then just helping his stools softern, as you may hear the milk is very thick, it doesnt even smell or taste like baby milk (yes lol i tasted it) and i'm sure my Lo was never really full up after drinking 5oz from it so it wasnt the milk for us i guess....Now he is on the aptimal first and he is a changed baby, he is now much fuller for longer and the milk tastes and smells like baby milk should, it isnt too thick for him to get out of the bottle and he gets to poo normally...
I dont know what your reason is for thinking of changing over milks but if your thinking becuase of your LO suffereing form constipation then from experience i would advise you give your LO cooled boiled water inbetween feeds and stay on the first milk, My LO has 1 or 2oz of cooled boiled water in between feeds and he hasnt since had constipation