SSIS Data Transfer vs. Linked Server
hi Linked servers in general not best practice.  I generally recommend against them.  To many reasons to explain here....this would be come a white paper.  hahahah  I have been doing ETL and data security for 25 years.  please consult an architect and don't ask people on internet claiming to be architect.  there are very few people out there with my level of experience.  there is never one answer either...it depends on many factors how you approach this. AND testing small amount of records is not valid test.  do more intense testing.   best of luck!