Size/Hardware buttons:  The SoundsGood wins the form factor battle with its standard-size, while the MiniJam juts out above and behind the Visor.  The MiniJam will be an issue for most carrying cases, while the SoundsGood will work with any case. Size has a significant impact on the hardware buttons, as the MiniJam's buttons are easier to get to and don't need to be pressed too hard to activate; they also have a dual function if you hold down a button for a few moments.  The SoundsGood has fewer buttons, but they are the most commonly used; it also uses a more convenient Volume wheel than the two button approach of the MiniJam.

Storage:  The MiniJam can hold as much as you can afford, allowing it to expand with your needs.  The MiniJam uses MultiMedia Cards (MMCs) for storage, while the SoundsGood uses internal Flash RAM.  The MiniJam also has 2 MB of Flash RAM for storing PalmOS data.

Weight:  Both modules are very light, with the MiniJam because of its extra size weighing 75% more than the SoundsGood.

Transfer Speed:  The SoundsGood blows the MiniJam away in this department, as the SoundsGood transfered files from the desktop to the Visor at 13.9 MB/min during testing -- almost 7 times faster.  Transferring a song took less than 20 seconds instead of two minutes as it does with the MiniJam.

Extra Features:  The MiniJam has the ability to customize the MiniJukeBox application through skins, so you can customize your on-screen buttons however you like.  The MiniJam can also store PalmOS data on its 2 MB of Flash RAM, and will have the ability to store data on its MMCs soon.  The SoundsGood has a neat waveform that you can display while listening to music, making it seem more like the modern desktop players that are available.

Multitasking:  Finally I can do more than one thing at a time on the Visor.  Both the MiniJam and SoundsGood will play music perfectly in the background while you are in another application, as all MP3 processing is done on the module itself.  I also ran PocketMark while listening to music and neither Springboard module lowered the rating while being used.  Both modules can also play music while HotSyncing, for the ultimate in multitasking!