I wasn't for a moment suggesting they weren't the same person (or at least a clone of the same person) . I'm just speculating on how Palpatine may have been able to hide his powers from the Jedi for so long, and how he has been able to train two sith apprentices on Coruscant whilst holding on to a very public position in office, and how has managed to keep his true identity hidden from Count Dooku his own apprentice? ,and I think there may be a little more to Darth Sidious' identity than just Palpatine in a dark hood.

and considering we are yet to have any groundbreaking surprises revealed in the trilogy, this may be it, It's not uncommon for a character to use a decoy in this trilogy Padme/Amidala has been using her handmaidens as decoys on many occasions