Don't do the power versions. It will only make Jerking MUCH harder when you come out of a harder Clean. Do Rack Jerks instead in your training to help fix your Jerks.
When a lifter has a good grasp of the full Snatch with consistent technique.
Why? To help the lifter pull strong in the 2nd pull mid way. I open up well but sometimes midway through the 2nd pull I am not really pulling on the bar. I'm getting under it. And also to keep the bar close to the lifter.
It's NEVER instead of full Snatches. It's always in addition.
Power Snatch should only be used for lifters who know how to Snatch properly. The biggest thing between a beginner and a good lifter and a elite lifter is speed under the bar. This should be the most fundamental thing a lifter should learn first.