Instrument plug-ins:

• MAS instruments support multiple MIDI input ports, whereas AU instruments do not. So for example, the MAS version of MachFive 2 will have four ports (64 channels) available while the AU version will have one port (16 channels). For either MAS or AU, you can always instantiate additional instances if you need more MIDI inputs.

• Most MAS instruments with multiple outputs use DP's busses, while AU instruments use their own bundles which are configured under the Bundles window > Instruments tab. (DP's included Model12 MAS plug-in is an exception; it uses an AU-like method for its outputs.)

  Since DP can have up to 99 stereo busses, this means there are potentially more outputs available to MAS plug-ins; AUs have a set number of auxiliary outputs, usually 8 or 16 stereo outputs in addition to the plug-in's main outputs.

  However, since DP's busses are shared between all MAS instruments, as well as any busses you may be using in your sequence, if you want to use multiple outputs from multiple MAS VIs in a busy sequence there are potentially fewer outputs available to each plug-in.

  Additionally, AU instruments bundles are configured in the Instruments tab of the Bundles window, keeping them separate from your regular busses; this can help clarify who the various bundles belong to. MAS instrument bundles are mixed in with your other busses under the Bus tab.

• Some MAS instruments have not yet been updated to take advantage of DP 6's VI pre-rendering and Bounce to Disk abilities. Check with the plug-in manufacturer for updates.

Effect plug-ins:

• As with instruments, some MAS effect plug-ins may not take advantage of DP's pre-rendering abilities. Check with the plug-in manufacturer for updates.

Both:

• When saving host presets (using the Presets menu in DP's Effects window), MAS and AU plug-ins use different preset file formats. If you want to use your presets in other AU-compatible hosts, use the AU version of the plug-in in DP so your presets will be saved in the standard .aupreset format. Note that if a plug-in uses its own plug-in management (where controls for saving & managing presets are in the plug-in GUI itself, e.g. some Waves plug-ins) this does not apply as the preset file format will usually be manufacturer-specific; check with the plug-in manufacturer for more information on any proprietary preset file formats.
• AU plug-ins cannot be organized in any way, beyond the automatic grouping by manufacturer. MAS plug-ins can be organized into folders in the Finder (/Library/Audio/Plug-ins/MAS).