All of the Spartan-6 LX devices supported in a particular package are pin-out compatible. All of the Spartan-6 LXT devices supported in a particular package are pin-out compatible. The Spartan-6 LX devices are not pin compatible with the Spartan-6 LXT devices. Pins that are not available in some of the devices are listed in the No Connects column of each table.
The LX25 device has BUFIO2 pin compatibility issue with other devices; see
(Xilinx Answer 34885)