The HoT and DoT nature of feral affinity synergizes exceptionally well as you can cycle back and forth between the two while maintaining excellent mobility and uptime. You can open with a rake, dump energy, and apply a rip in a few seconds and go back to HoTs while they are ticking away, and then jump back in cat with a full energy and repeat. It just has a very natural and good feeling flow.
Boomkin feels a lot more janky as you have to deal with the goofy eclipse system and are forced to hardcast to do damage.
Having said that there are definitely situations where balance affinity is better.