In theory, a desktop would be better. But not always. I have an older PRO-2052 that sounds absolutely WONDERFUL. It has a large, mostly-hollow case and the speaker on the top of the cabinet. You can hear it very clearly, even at lower volume levels, and it has a nice wide frequency response.
My brand new PRO-433, however, has the speaker mounted on the bottom of the unit. Can't hear that thing well at all, and the audio is rather tinny. I keep an external speaker plugged into it all the time.
Either one is better than my handheld scanner (PRO-60 - old!). If there is any level of ambient noise at all, the handheld has to be turned up so loud that it often starts distorting the audio. And the speaker is so small the audio is very tinny, with almost no low-frequency response at all.