I believe that his death in TROS could have been done better. Story wise? It works with the spirits of the Jedi empowering Rey to finally destroy the Sith Order once and for all. The problem? Between the sound effects and visual effects it falls a bit flat. Not to mention simply crossing lightsabers seems too easy for one such as Sidious. Not to mention a slight missed opportunity with Rey and Ben Solo destroying the Sith together.
In that case his death in ROTJ is pretty much a perfect one. Unexpected and satisfying. With a neat redemption arc by Vader to boot.