Just an idea and request for profile migration.
Piro-san found an article written in Japanese which explains why he/she keeps using Chrome.
In the article, one of the reasons is explained as that cannot access credit card information, cannot access passwords, etc which is stored in Chrome.
If he/she used Firefox with new profile, Firefox must have already offered profile migration from another browser. However, if it has been done, and sometimes they use Firefox sometimes, newer data after the migration won't be merged to Firefox's profile.
Therefore, it seems that Firefox should have "incremental" migration feature that imports newer bookmark/history/password/form fill data in background. Then, users can test newer Firefox with their latest private data.