I am working on the Differential Expression Analysis on RNA-Seq Data between tumor sample and normal sample, while my lecturer suggest me better use the raw expression data instead of using FPKM as expression unit , anyone could tell me why ? or what is the advantage for this ? 
If you want further details, you can visit Joshua Starmer youtube collection of videos

In this one, you can see details about [how DESeq2 normalize RNA-Seq data][1] from raw data

And in this one, [how does it edgeR][2]


  [1]: https://www.youtube.com/watch?v=UFB993xufUU
  [2]: https://www.youtube.com/watch?v=Wdt6jdi-NQo