More voiced dialog? Fascinating!
I'm too of the opinion that voice acting is often unnecessary and annoying, especially in more modern games. However, in this particular case my understanding is that they recorded full voice acting for the CD-ROM version of World of Xeen which they included in the Mac version (there is OS level support for the speech compression they used in Mac OS).
Then when it came to the DOS release, however, they had to cut content because of ineptitude, basically — they were not able to implement a similar speech compression scheme for DOS, and they did not want to ship the game on multiple CDs with uncompressed speech samples.
Similarly, the MT-32 driver in World of Xeen is bugged beyond recognition; it crashes the game left right center after a few minutes. That's not a DOSBox problem as the exact same behaviour is present on real hardware; it's a result of bad coding and/or insufficient testing.
In contrast, the Mac CD-ROM release contains audio recordings of the MIDI music played on a Roland MT-32 (the MIDI device the soundtrack was composed on). Admittedly, it's a little bit noisy, but it kinda adds to the atmosphere
I can't manage to dig up the Vogons (?) thread where this was discussed in detail, but basically these are the justifications for nominating the Mac release as the best version for World of Xeen (as in closest to the developers' intentions).
Of course, just playing the floppy DOS versions with AdLib sound and no speech is an equally valid choice, either for nostalgic or whatever other reasons.