Automatic waterer advantages:
Don’t have to fill.
Automatic waterer disadvantages:
Easy to break.
Tricky to clean.
Leak.
Can’t measure how much your horse is drinking.
If your horse needs water additives to entice drinking, the dilution will never be correct in an automatic waterer.
If your horse is a hay dunker,it gets very messy.
Water bucket advantages:
You can measure how much the horses are drinking.
Easy to clean.
Easy to transport to shows.
Easy to mix electrolytes or vinegar in the proper dilutions.
Easy to have a separate hay dunking bucket away from the drinking buckets.
Water bucket disadvantages:
More wasted water (use the water for plants or other uses).
It requires work.