I have both the Catalyst and the Sovereign stainless fermenter (similar to SS Brew Bucket, Anvil fermenter). To be honest I don't use my Catalyst anymore. I am 100% bucket fan.
Catalyst:
It has only 6 gallons and every batch results in blowoff from low headspace.
It's plastic so scratches happen, although I have never had an infection, that is a potential.
The fermenter has a weird shape, so applying any heating blanket is a little difficult.
There are no fermentation temp control options, so the only option is to place in ferm chamber, or rig together a chiller from other brands accessories. Carrying it is difficult.
Collecting yeast is super easy as is dumping trub, but I think trub dumps are a little overrated for home brewers.
transferring to keg or bottling is the best feature, no racking canes needed.
Adding the sampling port is nice for gravity readings.
Bucket:
Its stainless and can be cleaned with aggressive cleaners without issue need be.
Temperature control options are available for most, but also easy to add with weldless fittings. Ghetto rigging heating and cooling is easier as stainless conducts heat better for those who use swamp cooling methods.
Smaller profile, may fit in ferm chambers easier. Having handles makes easier to carry.
You can't harvest yeast until you rack the beer off the cake.
You can customize buckets since you can weld to it, or use weldless fittings.
Here is what I did to mine. I drilled the lid for 1.5" TC and have a blowoff tub thermowell on it. Works great. I also just ordered a TC lid with keg gas in so I can have o2 free transfers.
https://www.homebrewtalk.com/forum/threads/sovereign-stainless-fermentor.641995/#post-8306003
