In Health ts all in one place. 
But maybe you are just interested in that “fitbit-stuff”, thats ok.
For me the Watch delivers so much data that are collected in Health, so i try to store all data there. Because then 3th party apps have also access to them (if i allow). I found it difficult to export the data from fitbit.
Hi there. I use IFTTT to move data from Aria weigh-ins into Health. Works great!
+1 for Xiaomi – I’m very happy with the performance.
Side note: Xiaomi can be set up with different profiles for different users, which is a good idea if your scale is in a shared location. Our petsitter, who weighs considerably more than me, was using it and I had to go into Health and the Xiaomi app and delete their entries 
Do you have a link to the ifttt rule? Any drawbacks to using ifttt this way?