The Trek 1.2 is the "nicer" bike. While both are entry level road bikes, the 1.2 is spec'd with higher components and superior frame material. The major differences are in the fork material and drivetrain (shifters, derailleurs, etc...). The Defy 4 has a cro-moly steel fork. While this is not a intrinsically undesirable material, the 1.2 uses a carbon-fiber fork, far superior to steel. In regard to the drivetrain, the 1.2 is spec'd with components far higher-up in Shimano's product line then the Defy 4.
All is all, the Trek 1.2 is lighter, higher performance, and an all-around better bike then the Giant Defy 4.
Earth Trek ended on 2002-12-01.
The Story Trek - 2011 Light Where There Was No Light 1-12 was released on: USA: 2011
12
Star Trek - 1973 The Time Trap 1-12 is rated/received certificates of: USA:TV-Y7
Culture Trek Jamaica - 2002 was released on: USA: 12 November 2002
The Sleeping Giant was created in 2008-12.
Doshin the Giant was created on 1999-12-01.
The Giant of Marathon was created on 1959-12-03.
Giant Step was created in 1990.
Star Trek Klingon - 1996 VG is rated/received certificates of: UK:12 USA:M
Star Trek Deep Space Nine - 1993 The Begotten 5-12 was released on: USA: 27 January 1997
Star Trek Voyager - 1995 Resistance 2-12 was released on: USA: 27 November 1995 Germany: 31 January 1997