It would have been better if Sidious had landed on his feet and walked away before the Death Star blew up Seriously though, if Sion can survive being struck down with a lightsaber and continue to walk with all his bones fractured in little pieces, by all intents and purpouses, Sidious should have been able to survive a 1,000 foot fall without the need of a clone body (granted DE came out years befor KOTOR but I'm just sayin' lol).
the fall didn't kill sidious. his body was tossed into the reactor core and his body was burned apart, hence the explosion of energy.
Sion was holding his body together with hate alone, he had only been torn apart, broken, beaten, and etc. Sidious no longer had a body to hold together.