I thought the selection of voice on the PSR2000 is pretty good IF your voices happen to be on the FIRST page of that particular category.

They should also have the numeric keypad in addition to the category selection as in PSR2000. OR they allow the users to move the voice selections within the voice category and save that into the registration memory.

The category method is good if you want to switch quickly from say pianos to brass. Just press the category button for the trumpet and you can immediately play the brass. Provided that brass is the first entry. If not then you have to press another button to select the voice.

Worst case, just save it on registration memory and switch just by pressing one button.