Speaking from a design standpoint, the only reason a manufacturer places the wheels at the top is when the instrument in question has an 88 note keybed (as in each of the examples given).

Placing the wheels at the left side of an 88 note keybed renders the instrument way too long to fit inside any case. There is also the general belief that an 88-note instrument is purchased primarily for it's pianistic appeal and that performance wheels, when provided at all, are more of a "bonus feature" to facilitate optimal use of non-piano-type sounds.

Thus, a compromise will generally be accepted by buyer's of 88 note synths/controllers. In the case of 61 or 76-key instruments however, these restrictions do not apply. Case in point; the Equinox series was mentioned in the above quoted topic. While the Equinox 88 did have the wheels at the top, for the reasons stated, the Equinox 76 did not; they were back over at the left side of the keyboard.

[This message has been edited by Chris A (edited 11-19-2003).]