The E-MU Xboard 25 features:

25 full-size professional keys with Aftertouch - the Xboard 25 is a true performance controller with a high-quality synth-action keybed
Xboard Control™ software lets you easily create custom setups for your favorite hardware/software instruments
Advanced studio/live performance features, like Latch Mode for triggering drum loops, Snap Shot for instantaneous program changes, and many more
16 real-time controllers that can be assigned to the key performance parameters of all your favorite virtual instruments
Includes Proteus X LE Desktop Sound Module (for Windows) with over 1000 presets and Ableton Live Lite 4 for E-MU (for Windows)
USB, battery or AC powered - take your music anywhere
PC & Mac compatible - Windows XP, 2000 and Macintosh OS X drivers

The E-MU Xboard 49 features:

49 full-size professional keys with Aftertouch - the Xboard 49 is a true performance controller with a high-quality synth-action keybed
Xboard Control™ software lets you easily create custom setups for your favorite hardware/software instruments
Includes full version of E-MU's Proteus X2 Streaming Sound Module with over 3GB of sounds, as well as three additional sound libraries (Mo'Phatt X, Planet Earth X and Protean Drums X) for an additional 1,500 instruments (Windows only)
Advanced studio/live performance features, like Latch Mode for triggering drum loops, Snap Shot for instantaneous program changes, and many more
16 real-time controllers that can be assigned to the key performance parameters of all your favorite virtual instruments
USB, battery or AC powered - take your music anywhere
PC & Mac compatible - Windows XP, 2000, x64, Vista and Macintosh OS X drivers