Their strength is the same in DBZ but in GT, 17 turned into Super 17 then Goku killed him.
In Dragon Ball there is Android 8. In Dragon Ball Z there is Android 16, 17, 18, 19, and 20. Cell is also an organic android. In the Dragon Ball Z movies there is Android 13,14,15 and Super Android 13. In Dragon Ball GT there is a fusion between the dead Android 17 and another Android 17 to make Super 17.
Dragon Ball - 1986 Rematch 5-17 was released on: USA: 4 November 2003
Dragon Ball - 1986 Danger in the Air 2-17 was released on: USA: 5 March 2002
Dragon Ball - 1986 Prelude to Vengeance 4-17 was released on: USA: 29 September 2003
You never find out in any official Dragon Ball media. Also 17 died in GT.
Dragon Ball Z - 1989 Find the Dragon Balls - 6.2 was released on: USA: 17 September 2002
Android #18 is actually stronger than Android #17. Even though #17 was programmed slightly stronger than her, he was unable to use the 100% of his power (Dr. Gero's flaw, corrected on #18), making #18 the strongest of both twins. This was verified by Akira Toriyama himself during an interview.
the internet
Dragon Ball Z - 1989 The Saibamen Strike 1-17 was released on: USA: 8 February 1997
Dragon Ball Z - 1989 Vegeta Revived 2-17 was released on: USA: 8 November 1997
Dragon Ball Z - 1989 Rip in the Universe 7-17 was released on: USA: 11 November 2002
Dragon Ball Z - 1989 Dende's Demise 3-17 was released on: USA: 1 October 1999