As a rule, powder filler is less expensive than ready to use types of filler and can produce a more professional finish. But you need to add your own water and mix to the correct consistency first. And you can't save any leftover product once it's been mixed.
One key reason why professionals prefer to use powder filler is because most products tend to set and dry much faster than ready to use alternatives. Some even contain special additives, that are designed to accelerate drying times.
Choosing the best filler for the job always helps deliver the best possible results. And results will vary, depending on the type of powder filler you use. So the first thing you need to consider is the location and type of material that you're filling. Then contemplate speed. Think about how long each mixed product stays open before starting to set, does this meet your objective? Finally examine drying time, for example bear in mind how quickly you might want to start painting.