Hi,Please tell me what is the difference between GHS keyboard (Initial Touch) keys (MOXF8)
and Balanced Hammer Effect Keyboard (Initial Touch/Aftertouch) keys (Motif XF8) ?

Also I would like to know what are the main differences between MOXF8 and special edition Motif XF White? specifically with sounds, Arp, effects ,etc.  Thanks.

Differences between MOXF and Motif XF discussed at:
http://www.motifator.com/index.php/forum/viewthread/469959/

From the names, you can tell that GHS is graded, meaning that lower keys feel heavier and higher keys feel lighter, whereas the Balanced actions are, well, balanced, they feel the same everywhere. In that particular respect, the GHS is closer to an acoustic piano However the name--or that particular feature--doesn’t tell the whole story, as there are numerous other differences in how the actions are designed, and in fact, most people feel that the XF action feels better. The biggest advantage of the GHS action is that it is a lighter mechanism, allowing the keyboards to weigh less.

Both actions, as you mention, have Initial Touch, which is what is more generally called Velocity Sensitivity… the keyboard can tell how hard you are striking the keys, and reproduce the sound accordingly. (For example, on a piano sound, when you hit a key harder, it is louder.) The XF keyboard also has aftertouch, which means that, after you strike a key, you can press it harder to generate an effect (often used for things like introducing vibrato to a sound, or making it brighter).