Performances - Power query Service vs power query desktop

Hi BI-1294 

They are definitely not the same. One is using cloud resources and the other using resoruces on your local computer. I personally have found it best and better perfornance developing the query / M script locally, then export or copy and paste into the dataflow. 
Hope this helps.

Hi BI-1294 ,

The performance of Power Query in service will depend on what licence type you're using. You'll get the best performance on a Premium Capacity Workspace, next on a Premium Per User, and finally a Pro workspace. Performance of Power Query in Power BI desktop will depend on how powerful your PC is as some transforms may be running on your PC.  Finally it also depends on how responsive your data server is that feeds the Data. For instance if you have a slow SQL server, or are getting data from Sharepoint Online (which can be slow) or other overloaded resource, your Power Query, whether On-premise or Server may be slowed by that.

Generally I've found a  Pro workspace to be slower than my PC at Power Query, but PPU and Premium Capacity slightly faster. But it depends on many things so "your mileage may vary".

Hope this helps

Stuart