Plenty of small quality of life features that sync for reddit had which jerboa doesn't. Posting from alt accounts from the comment window, extensive customization options, material design UI, different themes and settings for different accounts, and plenty of others that I don't remember off the top of my head.
Jerboa is by no means bad but as a long time sync user, I'm really excited to have the familiarity of sync back.
Jerboa is my winning app since I signed up to Lemmy. However, I'm still not totally pleased with it and find myself switching between that and thunder. I'm excited Sync is coming here and I'll definitely preregister but I'm pining for my previous Boost